[PATCH] Implement SRFI-105 curly infix expressions.

[PATCH] Implement SRFI-105 curly infix expressions.

[Mark H Weaver]

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Hello all,

Here's a patch to implement curly infix expressions in Guile's core
reader, based on the current draft of SRFI-105.  It depends upon the
per-port reader options patches that I posted here a few minutes ago.

With this patch, although curly-infix expressions are not enabled by
default, they will be automatically enabled on a per-port basis when
'read' encounters the "#!curly-infix" reader directive.  They can also
be enabled globally by enabling the 'curly-infix' reader option.

David: if you would be willing to produce a set of SRFI-105 expressions
(along with their s-expression equivalents) to add to our test suite,
that would be very helpful.

It's probably not appropriate to commit this patch before SRFI-105 has
been finalized, but in the meantime here's a (hopefully) complete patch
set for your enjoyment.

Comments and suggestions solicited,

      Mark



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From 57a4ae1eb7f58103574525c7e727ff08d44f18ec Mon Sep 17 00:00:00 2001
From: Mark H Weaver <mhw@netris.org>
Date: Sun, 14 Oct 2012 04:09:01 -0400
Subject: [PATCH] Implement SRFI-105 curly infix expressions.

* libguile/private-options.h: Add SCM_CURLY_INFIX_P macro, and increment
  SCM_N_READ_OPTIONS.

* libguile/read.c (scm_read_opts): Add curly-infix reader option.
  (scm_t_read_opts): Add curly_infix_p field.
  (init_read_options): Initialize new curly_infix_p field.
  (CHAR_IS_DELIMITER): Add '{' and '}' as delimiters if curly_infix_p
  is set.

  (set_per_port_curly_infix_p): New internal static function.

  (scm_read_shebang): Handle '#!curly-infix' reader directive.

  (scm_read, scm_read_keyword, scm_read_vector, scm_read_bytevector):
  Pass new 'neoteric_p' argument to subroutines where needed.

  (scm_read_expression_1): New internal static function, which contains
  the code that was previously in 'scm_read_expression'.  Handle curly
  braces when curly_infix_p is set.  Pass new 'neoteric_p' argument to
  subroutines where needed.

  (scm_read_expression): Add 'neoteric_p' argument.  New function body
  to handle neoteric expressions where appropriate.

  (scm_read_sexp): Add 'neoteric_p' argument.  Handle curly infix
  expressions, converting them to normal s-expressions.

  (flush_ws, scm_read_commented_expression, scm_read_sharp,
  scm_read_quote, scm_read_syntax): Add 'neoteric_p' argument.
  Pass new 'neoteric_p' argument to subroutines where needed.

* doc/ref/srfi-modules.texi (SRFI-105): Add stub doc for SRFI-105.

* doc/ref/api-evaluation.texi (Scheme Read): Add documentation for the
  'curly-infix' read option and the '#!curly-infix' reader directive.

* doc/ref/api-options.texi (Runtime Options): Add 'curly-infix' to the
  list of read options.

* test-suite/Makefile.am: Add tests/srfi-105.test.

* test-suite/tests/srfi-105.test: New file.
---
 doc/ref/api-evaluation.texi    |   10 +-
 doc/ref/api-options.texi       |    1 +
 doc/ref/srfi-modules.texi      |   14 +++
 libguile/private-options.h     |    3 +-
 libguile/read.c                |  212 ++++++++++++++++++++++++++++++++--------
 test-suite/Makefile.am         |    1 +
 test-suite/tests/srfi-105.test |   67 +++++++++++++
 7 files changed, 260 insertions(+), 48 deletions(-)
 create mode 100644 test-suite/tests/srfi-105.test

diff --git a/doc/ref/api-evaluation.texi b/doc/ref/api-evaluation.texi
index 9eccb39..245d4e0 100644
--- a/doc/ref/api-evaluation.texi
+++ b/doc/ref/api-evaluation.texi
@@ -338,13 +338,15 @@ r6rs-hex-escapes  no    Use R6RS variable-length character and string hex escape
 square-brackets   yes   Treat `[' and `]' as parentheses, for R6RS compatibility.
 hungry-eol-escapes no   In strings, consume leading whitespace after an
                         escaped end-of-line.
+curly-infix       no    Support SRFI-105 curly infix expressions.
 @end smalllisp
 
 Note that Guile also includes a preliminary mechanism for overriding
-read options on a per-port basis.  Currently, the only read option that
-is overridden in this way is the @code{case-insensitive} option, which
-is set or unset when the reader encounters the special directives
-@code{#!fold-case} or @code{#!no-fold-case}.  There is currently no
+read options on a per-port basis.  The only read options that can
+currently be overridden in this way are the @code{case-insensitive} and
+@code{curly-infix} options, which are set (or unset) when the reader
+encounters the special directives @code{#!fold-case},
+@code{#!no-fold-case}, or @code{#!curly-infix}.  There is currently no
 other way to access or set these per-port read options.
 
 The boolean options may be toggled with @code{read-enable} and
diff --git a/doc/ref/api-options.texi b/doc/ref/api-options.texi
index f635978..1734318 100644
--- a/doc/ref/api-options.texi
+++ b/doc/ref/api-options.texi
@@ -390,6 +390,7 @@ r6rs-hex-escapes  no    Use R6RS variable-length character and string hex escape
 square-brackets   yes   Treat `[' and `]' as parentheses, for R6RS compatibility.
 hungry-eol-escapes no   In strings, consume leading whitespace after an
                         escaped end-of-line.
+curly-infix       no    Support SRFI-105 curly infix expressions.
 scheme@@(guile-user) [1]> (read-enable 'case-insensitive)
 $2 = (square-brackets keywords #f case-insensitive positions)
 scheme@@(guile-user) [1]> ,q
diff --git a/doc/ref/srfi-modules.texi b/doc/ref/srfi-modules.texi
index ba701a2..bf7b3f2 100644
--- a/doc/ref/srfi-modules.texi
+++ b/doc/ref/srfi-modules.texi
@@ -54,6 +54,7 @@ get the relevant SRFI documents from the SRFI home page
 * SRFI-69::                     Basic hash tables.
 * SRFI-88::                     Keyword objects.
 * SRFI-98::                     Accessing environment variables.
+* SRFI-105::                    Curly infix expressions.
 @end menu
 
 
@@ -4469,6 +4470,19 @@ Returns the names and values of all the environment variables as an
 association list in which both the keys and the values are strings.
 @end deffn
 
+@node SRFI-105
+@subsection SRFI-105 Curly infix expressions.
+@cindex SRFI-105
+@cindex curly infix expressions
+@cindex curly-infix
+
+Guile's built-in reader includes support for SRFI-105 curly infix
+expressions.  To enable curly infix expressions, place the reader
+directive @code{#!curly-infix} near the top of each source file.  To
+globally enable curly infix expressions in Guile's reader, set the
+@code{curly-infix} reader option.  For more information on reader
+options, @xref{Scheme Read}.
+
 @c srfi-modules.texi ends here
 
 @c Local Variables:
diff --git a/libguile/private-options.h b/libguile/private-options.h
index 9d2d43c..ed0f314 100644
--- a/libguile/private-options.h
+++ b/libguile/private-options.h
@@ -67,7 +67,8 @@ SCM_INTERNAL scm_t_option scm_read_opts[];
 #define SCM_R6RS_ESCAPES_P     scm_read_opts[4].val
 #define SCM_SQUARE_BRACKETS_P  scm_read_opts[5].val
 #define SCM_HUNGRY_EOL_ESCAPES_P scm_read_opts[6].val
+#define SCM_CURLY_INFIX_P      scm_read_opts[7].val
 
-#define SCM_N_READ_OPTIONS 6
+#define SCM_N_READ_OPTIONS 7
 
 #endif  /* PRIVATE_OPTIONS */ 
diff --git a/libguile/read.c b/libguile/read.c
index da51a05..eebdbe2 100644
--- a/libguile/read.c
+++ b/libguile/read.c
@@ -62,6 +62,8 @@ SCM_GLOBAL_SYMBOL (scm_sym_dot, ".");
 SCM_SYMBOL (scm_keyword_prefix, "prefix");
 SCM_SYMBOL (scm_keyword_postfix, "postfix");
 SCM_SYMBOL (sym_nil, "nil");
+SCM_SYMBOL (sym_nfx, "nfx");
+SCM_SYMBOL (sym_bracket_apply, "$bracket-apply$");
 
 scm_t_option scm_read_opts[] = {
   { SCM_OPTION_BOOLEAN, "copy", 0,
@@ -78,6 +80,8 @@ scm_t_option scm_read_opts[] = {
     "Treat `[' and `]' as parentheses, for R6RS compatibility."},
   { SCM_OPTION_BOOLEAN, "hungry-eol-escapes", 0,
     "In strings, consume leading whitespace after an escaped end-of-line."},
+  { SCM_OPTION_BOOLEAN, "curly-infix", 0,
+    "Support SRFI-105 curly infix expressions."},
   { 0, },
 };
 
@@ -96,6 +100,7 @@ typedef struct {
   char r6rs_escapes_p;
   char square_brackets_p;
   char hungry_eol_escapes_p;
+  char curly_infix_p;
 } scm_t_read_opts;
 
 /*
@@ -129,7 +134,8 @@ SCM_SYMBOL (sym_read_option_overrides, "%read-option-overrides%");
 #define OVERRIDE_SHIFT_R6RS_ESCAPES_P         8
 #define OVERRIDE_SHIFT_SQUARE_BRACKETS_P     10
 #define OVERRIDE_SHIFT_HUNGRY_EOL_ESCAPES_P  12
-#define OVERRIDES_SHIFT_END                  14
+#define OVERRIDE_SHIFT_CURLY_INFIX_P         14
+#define OVERRIDES_SHIFT_END                  16
 
 #define OVERRIDES_ALL_DEFAULTS  ((1UL << OVERRIDES_SHIFT_END) - 1)
 #define OVERRIDES_MAX_VALUE     OVERRIDES_ALL_DEFAULTS
@@ -168,6 +174,15 @@ set_per_port_case_insensitive_p (SCM port, scm_t_read_opts *opts, int value)
   set_per_port_read_option (port, OVERRIDE_SHIFT_CASE_INSENSITIVE_P, value);
 }
 
+/* Set curly_infix_p on a per-port basis. */
+static void
+set_per_port_curly_infix_p (SCM port, scm_t_read_opts *opts, int value)
+{
+  value = !!value;
+  opts->curly_infix_p = value;
+  set_per_port_read_option (port, OVERRIDE_SHIFT_CURLY_INFIX_P, value);
+}
+
 /* Initialize the internal read options structure from the global and
    per-port read options. */
 static void
@@ -214,6 +229,7 @@ init_read_options (SCM port, scm_t_read_opts *opts)
   RESOLVE_BOOLEAN_OPTION(R6RS_ESCAPES_P,       r6rs_escapes_p);
   RESOLVE_BOOLEAN_OPTION(SQUARE_BRACKETS_P,    square_brackets_p);
   RESOLVE_BOOLEAN_OPTION(HUNGRY_EOL_ESCAPES_P, hungry_eol_escapes_p);
+  RESOLVE_BOOLEAN_OPTION(CURLY_INFIX_P,        curly_infix_p);
 
 #undef RESOLVE_BOOLEAN_OPTION
 }
@@ -330,7 +346,8 @@ scm_i_read_hash_procedures_set_x (SCM value)
 
 #define CHAR_IS_DELIMITER(c)                                    \
   (CHAR_IS_R5RS_DELIMITER (c)                                   \
-   || (opts->square_brackets_p && ((c) == ']' || (c) == '[')))
+   || (opts->square_brackets_p && ((c) == ']' || (c) == '['))   \
+   || (opts->curly_infix_p     && ((c) == '}' || (c) == '{')))
 
 /* Exponent markers, as defined in section 7.1.1 of R5RS, ``Lexical
    Structure''.  */
@@ -341,7 +358,8 @@ scm_i_read_hash_procedures_set_x (SCM value)
 /* Read an SCSH block comment.  */
 static SCM scm_read_scsh_block_comment (scm_t_wchar, SCM);
 static SCM scm_read_r6rs_block_comment (scm_t_wchar, SCM);
-static SCM scm_read_commented_expression (scm_t_wchar, SCM, scm_t_read_opts *);
+static SCM scm_read_commented_expression (scm_t_wchar, SCM,
+                                          scm_t_read_opts *, int);
 static SCM scm_read_shebang (scm_t_wchar, SCM, scm_t_read_opts *);
 static SCM scm_get_hash_procedure (int);
 
@@ -427,7 +445,7 @@ read_complete_token (SCM port, scm_t_read_opts *opts,
 /* Skip whitespace from PORT and return the first non-whitespace character
    read.  Raise an error on end-of-file.  */
 static int
-flush_ws (SCM port, scm_t_read_opts *opts, const char *eoferr)
+flush_ws (SCM port, scm_t_read_opts *opts, int neoteric_p, const char *eoferr)
 {
   scm_t_wchar c;
   while (1)
@@ -467,7 +485,7 @@ flush_ws (SCM port, scm_t_read_opts *opts, const char *eoferr)
 	    scm_read_shebang (c, port, opts);
 	    break;
 	  case ';':
-	    scm_read_commented_expression (c, port, opts);
+	    scm_read_commented_expression (c, port, opts, neoteric_p);
 	    break;
 	  case '|':
 	    if (scm_is_false (scm_get_hash_procedure (c)))
@@ -498,9 +516,10 @@ flush_ws (SCM port, scm_t_read_opts *opts, const char *eoferr)
 \f
 /* Token readers.  */
 
-static SCM scm_read_expression (SCM port, scm_t_read_opts *opts);
+static SCM scm_read_expression (SCM port, scm_t_read_opts *opts,
+                                int neoteric_p);
 static SCM scm_read_sharp (int chr, SCM port, scm_t_read_opts *opts,
-                           long line, int column);
+                           int neoteric_p, long line, int column);
 
 
 static SCM
@@ -513,31 +532,35 @@ maybe_annotate_source (SCM x, SCM port, scm_t_read_opts *opts,
 }
 
 static SCM
-scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
+scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts, int neoteric_p)
 #define FUNC_NAME "scm_i_lreadparen"
 {
   int c;
   SCM tmp, tl, ans = SCM_EOL;
-  const int terminating_char = ((chr == '[') ? ']' : ')');
+  const int curly_infix_p = (chr == '{');
+  const int terminating_char = ((chr == '{') ? '}'
+                                : ((chr == '[') ? ']'
+                                   : ')'));
 
   /* Need to capture line and column numbers here. */
   long line = SCM_LINUM (port);
   int column = SCM_COL (port) - 1;
 
-  c = flush_ws (port, opts, FUNC_NAME);
+  c = flush_ws (port, opts, neoteric_p, FUNC_NAME);
   if (terminating_char == c)
     return SCM_EOL;
 
   scm_ungetc (c, port);
-  tmp = scm_read_expression (port, opts);
+  tmp = scm_read_expression (port, opts, neoteric_p);
 
   /* Note that it is possible for scm_read_expression to return
      scm_sym_dot, but not as part of a dotted pair: as in #{.}#.  So
      check that it's a real dot by checking `c'.  */
   if (c == '.' && scm_is_eq (scm_sym_dot, tmp))
     {
-      ans = scm_read_expression (port, opts);
-      if (terminating_char != (c = flush_ws (port, opts, FUNC_NAME)))
+      ans = scm_read_expression (port, opts, neoteric_p);
+      if (terminating_char != (c = flush_ws (port, opts, neoteric_p,
+                                             FUNC_NAME)))
 	scm_i_input_error (FUNC_NAME, port, "missing close paren",
 			   SCM_EOL);
       return ans;
@@ -546,28 +569,30 @@ scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
   /* Build the head of the list structure. */
   ans = tl = scm_cons (tmp, SCM_EOL);
 
-  while (terminating_char != (c = flush_ws (port, opts, FUNC_NAME)))
+  while (terminating_char != (c = flush_ws (port, opts, neoteric_p,
+                                            FUNC_NAME)))
     {
       SCM new_tail;
 
-      if (c == ')' || (opts->square_brackets_p && c == ']'))
+      if (c == ')' || (opts->square_brackets_p && c == ']')
+          || (opts->curly_infix_p && c == '}'))
         scm_i_input_error (FUNC_NAME, port,
                            "in pair: mismatched close paren: ~A",
                            scm_list_1 (SCM_MAKE_CHAR (c)));
 
       scm_ungetc (c, port);
-      tmp = scm_read_expression (port, opts);
+      tmp = scm_read_expression (port, opts, neoteric_p);
 
       /* See above note about scm_sym_dot.  */
       if (c == '.' && scm_is_eq (scm_sym_dot, tmp))
 	{
-	  SCM_SETCDR (tl, scm_read_expression (port, opts));
+	  SCM_SETCDR (tl, scm_read_expression (port, opts, neoteric_p));
 
-	  c = flush_ws (port, opts, FUNC_NAME);
+	  c = flush_ws (port, opts, neoteric_p, FUNC_NAME);
 	  if (terminating_char != c)
 	    scm_i_input_error (FUNC_NAME, port,
 			       "in pair: missing close paren", SCM_EOL);
-	  goto exit;
+	  break;
 	}
 
       new_tail = scm_cons (tmp, SCM_EOL);
@@ -575,8 +600,51 @@ scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
       tl = new_tail;
     }
 
- exit:
-  return maybe_annotate_source (ans, port, opts, line, column);
+  if (curly_infix_p)
+    {
+      int len = scm_ilength (ans);
+
+      if (len == 1)
+        ans = scm_car (ans);
+      else if (len == 2)
+        ;  /* Leave the list unchanged */
+      else if (len >= 3 && (len & 1))
+        {
+          SCM op = scm_cadr (ans);
+
+          /* Verify that all infix operators are 'equal?' */
+          for (tl = scm_cdddr (ans); ; tl = scm_cddr (tl))
+            {
+              if (scm_is_null (tl))
+                {
+                  tl = ans;
+
+                  /* Convert simple curly-infix list to prefix */
+                  while (scm_is_pair (scm_cdr (tl)))
+                    {
+                      tmp = scm_cddr (tl);
+                      SCM_SETCDR (tl, tmp);
+                      tl = tmp;
+                    }
+                  ans = scm_cons (op, ans);
+                  break;
+                }
+              else if (scm_is_false (scm_equal_p (op, scm_car (tl))))
+                {
+                  /* Mixed curly-infix list */
+                  ans = scm_cons (sym_nfx, ans);
+                  break;
+                }
+            }
+        }
+      else
+        ans = scm_cons (sym_nfx, ans);  /* Mixed curly-infix list */
+    }
+
+  if (SCM_NIMP (ans))
+    return maybe_annotate_source (ans, port, opts, line, column);
+  else
+    return ans;
 }
 #undef FUNC_NAME
 
@@ -875,7 +943,7 @@ scm_read_number_and_radix (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
 #undef FUNC_NAME
 
 static SCM
-scm_read_quote (int chr, SCM port, scm_t_read_opts *opts)
+scm_read_quote (int chr, SCM port, scm_t_read_opts *opts, int neoteric_p)
 {
   SCM p;
   long line = SCM_LINUM (port);
@@ -912,7 +980,7 @@ scm_read_quote (int chr, SCM port, scm_t_read_opts *opts)
       abort ();
     }
 
-  p = scm_cons2 (p, scm_read_expression (port, opts), SCM_EOL);
+  p = scm_cons2 (p, scm_read_expression (port, opts, neoteric_p), SCM_EOL);
   return maybe_annotate_source (p, port, opts, line, column);
 }
 
@@ -922,7 +990,7 @@ SCM_SYMBOL (sym_unsyntax, "unsyntax");
 SCM_SYMBOL (sym_unsyntax_splicing, "unsyntax-splicing");
 
 static SCM
-scm_read_syntax (int chr, SCM port, scm_t_read_opts *opts)
+scm_read_syntax (int chr, SCM port, scm_t_read_opts *opts, int neoteric_p)
 {
   SCM p;
   long line = SCM_LINUM (port);
@@ -959,7 +1027,7 @@ scm_read_syntax (int chr, SCM port, scm_t_read_opts *opts)
       abort ();
     }
 
-  p = scm_cons2 (p, scm_read_expression (port, opts), SCM_EOL);
+  p = scm_cons2 (p, scm_read_expression (port, opts, neoteric_p), SCM_EOL);
   return maybe_annotate_source (p, port, opts, line, column);
 }
 
@@ -1128,7 +1196,7 @@ scm_read_keyword (int chr, SCM port, scm_t_read_opts *opts)
      to adapt to the delimiters currently valid of symbols.
 
      XXX: This implementation allows sloppy syntaxes like `#:  key'.  */
-  symbol = scm_read_expression (port, opts);
+  symbol = scm_read_expression (port, opts, 0);
   if (!scm_is_symbol (symbol))
     scm_i_input_error ("scm_read_keyword", port,
 		       "keyword prefix `~a' not followed by a symbol: ~s",
@@ -1145,8 +1213,9 @@ scm_read_vector (int chr, SCM port, scm_t_read_opts *opts,
      guarantee that it's going to do what we want.  After all, this is an
      implementation detail of `scm_read_vector ()', not a desirable
      property.  */
-  return maybe_annotate_source (scm_vector (scm_read_sexp (chr, port, opts)),
-                                port, opts, line, column);
+  return maybe_annotate_source
+    (scm_vector (scm_read_sexp (chr, port, opts, 0)),
+     port, opts, line, column);
 }
 
 static SCM
@@ -1184,7 +1253,7 @@ scm_read_bytevector (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
     goto syntax;
 
   return maybe_annotate_source
-    (scm_u8_list_to_bytevector (scm_read_sexp (chr, port, opts)),
+    (scm_u8_list_to_bytevector (scm_read_sexp (chr, port, opts, 0)),
      port, opts, line, column);
 
  syntax:
@@ -1267,6 +1336,8 @@ scm_read_shebang (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
             set_per_port_case_insensitive_p (port, opts, 1);
           else if (0 == strcmp ("no-fold-case", name))
             set_per_port_case_insensitive_p (port, opts, 0);
+          else if (0 == strcmp ("curly-infix", name))
+            set_per_port_curly_infix_p (port, opts, 1);
           else
             break;
 
@@ -1318,16 +1389,16 @@ scm_read_r6rs_block_comment (scm_t_wchar chr, SCM port)
 
 static SCM
 scm_read_commented_expression (scm_t_wchar chr, SCM port,
-                               scm_t_read_opts *opts)
+                               scm_t_read_opts *opts, int neoteric_p)
 {
   scm_t_wchar c;
   
-  c = flush_ws (port, opts, (char *) NULL);
+  c = flush_ws (port, opts, neoteric_p, (char *) NULL);
   if (EOF == c)
     scm_i_input_error ("read_commented_expression", port,
                        "no expression after #; comment", SCM_EOL);
   scm_ungetc (c, port);
-  scm_read_expression (port, opts);
+  scm_read_expression (port, opts, neoteric_p);
   return SCM_UNSPECIFIED;
 }
 
@@ -1456,7 +1527,7 @@ scm_read_sharp_extension (int chr, SCM port, scm_t_read_opts *opts)
    among the above token readers.   */
 static SCM
 scm_read_sharp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
-                long line, int column)
+                int neoteric_p, long line, int column)
 #define FUNC_NAME "scm_lreadr"
 {
   SCM result;
@@ -1531,11 +1602,11 @@ scm_read_sharp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
     case '!':
       return (scm_read_shebang (chr, port, opts));
     case ';':
-      return (scm_read_commented_expression (chr, port, opts));
+      return (scm_read_commented_expression (chr, port, opts, neoteric_p));
     case '`':
     case '\'':
     case ',':
-      return (scm_read_syntax (chr, port, opts));
+      return (scm_read_syntax (chr, port, opts, neoteric_p));
     case 'n':
       return (scm_read_nil (chr, port, opts));
     default:
@@ -1563,8 +1634,8 @@ scm_read_sharp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
 #undef FUNC_NAME
 
 static SCM
-scm_read_expression (SCM port, scm_t_read_opts *opts)
-#define FUNC_NAME "scm_read_expression"
+scm_read_expression_1 (SCM port, scm_t_read_opts *opts, int neoteric_p)
+#define FUNC_NAME "scm_read_expression_1"
 {
   while (1)
     {
@@ -1580,23 +1651,34 @@ scm_read_expression (SCM port, scm_t_read_opts *opts)
 	case ';':
 	  (void) scm_read_semicolon_comment (chr, port);
 	  break;
+        case '{':
+          if (opts->curly_infix_p)
+            return (scm_read_sexp (chr, port, opts, 1));
+          else
+            return (scm_read_mixed_case_symbol (chr, port, opts));
+        case '}':
+          if (opts->curly_infix_p)
+            scm_i_input_error (FUNC_NAME, port, "unexpected \"}\"", SCM_EOL);
+          else
+            return (scm_read_mixed_case_symbol (chr, port, opts));
 	case '[':
           if (!opts->square_brackets_p)
             return (scm_read_mixed_case_symbol (chr, port, opts));
           /* otherwise fall through */
 	case '(':
-	  return (scm_read_sexp (chr, port, opts));
+	  return (scm_read_sexp (chr, port, opts, neoteric_p));
 	case '"':
 	  return (scm_read_string (chr, port, opts));
 	case '\'':
 	case '`':
 	case ',':
-	  return (scm_read_quote (chr, port, opts));
+	  return (scm_read_quote (chr, port, opts, neoteric_p));
 	case '#':
 	  {
             long line  = SCM_LINUM (port);
             int column = SCM_COL (port) - 1;
-	    SCM result = scm_read_sharp (chr, port, opts, line, column);
+            SCM result = scm_read_sharp (chr, port, opts, neoteric_p,
+                                         line, column);
 	    if (scm_is_eq (result, SCM_UNSPECIFIED))
 	      /* We read a comment or some such.  */
 	      break;
@@ -1614,7 +1696,8 @@ scm_read_expression (SCM port, scm_t_read_opts *opts)
 	  return SCM_EOF_VAL;
 	case ':':
 	  if (opts->keyword_style == KEYWORD_STYLE_PREFIX)
-	    return scm_symbol_to_keyword (scm_read_expression (port, opts));
+	    return scm_symbol_to_keyword
+              (scm_read_expression (port, opts, neoteric_p));
 	  /* Fall through.  */
 
 	default:
@@ -1630,6 +1713,49 @@ scm_read_expression (SCM port, scm_t_read_opts *opts)
 }
 #undef FUNC_NAME
 
+static SCM
+scm_read_expression (SCM port, scm_t_read_opts *opts, int neoteric_p)
+#define FUNC_NAME "scm_read_expression"
+{
+  if (!neoteric_p)
+    return scm_read_expression_1 (port, opts, 0);
+  else
+    {
+      long line = SCM_LINUM (port);
+      int column = SCM_COL (port) - 1;
+      SCM expr = scm_read_expression_1 (port, opts, 1);
+
+      for (;;)
+        {
+          int chr = scm_getc (port);
+
+          if (chr == '(')
+            expr = scm_cons (expr, scm_read_sexp (chr, port, opts, 1));
+          else if (chr == '[')
+            expr = scm_cons (sym_bracket_apply,
+                             scm_cons (expr,
+                                       scm_read_sexp (chr, port, opts, 1)));
+          else if (chr == '{')
+            {
+              SCM arg = scm_read_sexp (chr, port, opts, 1);
+
+              if (scm_is_null (arg))
+                expr = scm_list_1 (expr);
+              else
+                expr = scm_list_2 (expr, arg);
+            }
+          else
+            {
+              scm_ungetc (chr, port);
+              break;
+            }
+          maybe_annotate_source (expr, port, opts, line, column);
+        }
+      return expr;
+    }
+}
+#undef FUNC_NAME
+
 \f
 /* Actual reader.  */
 
@@ -1649,12 +1775,12 @@ SCM_DEFINE (scm_read, "read", 0, 1, 0,
 
   init_read_options (port, &opts);
 
-  c = flush_ws (port, &opts, (char *) NULL);
+  c = flush_ws (port, &opts, 0, (char *) NULL);
   if (EOF == c)
     return SCM_EOF_VAL;
   scm_ungetc (c, port);
 
-  return (scm_read_expression (port, &opts));
+  return (scm_read_expression (port, &opts, 0));
 }
 #undef FUNC_NAME
 
diff --git a/test-suite/Makefile.am b/test-suite/Makefile.am
index 168e799..a843fcd 100644
--- a/test-suite/Makefile.am
+++ b/test-suite/Makefile.am
@@ -136,6 +136,7 @@ SCM_TESTS = tests/00-initial-env.test		\
 	    tests/srfi-67.test			\
 	    tests/srfi-69.test			\
 	    tests/srfi-88.test			\
+	    tests/srfi-105.test			\
 	    tests/srfi-4.test			\
 	    tests/srfi-9.test			\
 	    tests/statprof.test			\
diff --git a/test-suite/tests/srfi-105.test b/test-suite/tests/srfi-105.test
new file mode 100644
index 0000000..4e25634
--- /dev/null
+++ b/test-suite/tests/srfi-105.test
@@ -0,0 +1,67 @@
+;;;; srfi-105.test --- Test suite for Guile's SRFI-105 reader. -*- scheme -*-
+;;;;
+;;;; Copyright (C) 2012 Free Software Foundation, Inc.
+;;;;
+;;;; This library is free software; you can redistribute it and/or
+;;;; modify it under the terms of the GNU Lesser General Public
+;;;; License as published by the Free Software Foundation; either
+;;;; version 3 of the License, or (at your option) any later version.
+;;;;
+;;;; This library is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;;; Lesser General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU Lesser General Public
+;;;; License along with this library; if not, write to the Free Software
+;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+#!curly-infix
+
+(define-module (test-srfi-105)
+  #:use-module (test-suite lib)
+  #:use-module (srfi srfi-1))
+
+(with-test-prefix "curly-infix"
+  (pass-if (equal? '{n <= 5}                '(<= n 5)))
+  (pass-if (equal? '{a + b + c}             '(+ a b c)))
+  (pass-if (equal? '{x ,op y ,op z}         '(,op x y z)))
+  (pass-if (equal? '{a * {b + c}}           '(* a (+ b c))))
+  (pass-if (equal? '{x eqv? `a}             '(eqv? x `a)))
+  (pass-if (equal? '{(- a) / b}             '(/ (- a) b)))
+  (pass-if (equal? '{-(a) / b}              '(/ (- a) b)))
+  (pass-if (equal? '{(f a b) + (g h)}       '(+ (f a b) (g h))))
+  (pass-if (equal? '{f(a b) + g(h)}         '(+ (f a b) (g h))))
+  (pass-if (equal? '{a + f(b) + x}          '(+ a (f b) x)))
+  (pass-if (equal? '{{a > 0} and {b >= 1}}  '(and (> a 0) (>= b 1))))
+  (pass-if (equal? '{'f(x)}                 '(quote (f x))))
+  ;(pass-if (equal? '#1=f(#1#)               '#1=(f #1#)))
+  (pass-if (equal? '{length(x) >= 6}        '(>= (length x) 6)))
+
+  (pass-if (equal? '{}                      '()))
+  (pass-if (equal? '{e}                     'e))
+  (pass-if (equal? '{e1 e2}                 '(e1 e2)))
+
+  (pass-if (equal? '{a . t}                 '(nfx a . t)))
+  (pass-if (equal? '{a b . t}               '(nfx a b . t)))
+  (pass-if (equal? '{a b c . t}             '(nfx a b c . t)))
+  (pass-if (equal? '{a b c d . t}           '(nfx a b c d . t)))
+  (pass-if (equal? '{a + b +}               '(nfx a + b +)))
+  (pass-if (equal? '{a + b + c +}           '(nfx a + b + c +)))
+  (pass-if (equal? '{q + r * s}             '(nfx q + r * s)))
+  ;(pass-if (equal? '#1={a + . #1#}          '(nfx . #1=(a + . #1#))))
+
+  (pass-if (equal? '{e()}                   '(e)))
+  (pass-if (equal? '{e{}}                   '(e)))
+  (pass-if (equal? '{e(1)}                  '(e 1)))
+  (pass-if (equal? '{e{1}}                  '(e 1)))
+  (pass-if (equal? '{e(1 2)}                '(e 1 2)))
+  (pass-if (equal? '{e{1 2}}                '(e (1 2))))
+  (pass-if (equal? '{f{n - 1}}              '(f (- n 1))))
+  (pass-if (equal? '{f{n - 1}(x)}           '((f (- n 1)) x)))
+  (pass-if (equal? '{g{- x}}                '(g (- x))))
+  (pass-if (equal? '{( . e)}                'e))
+
+  (pass-if (equal? '{e[]}                   '($bracket-apply$ e)))
+  (pass-if (equal? '{e[1 2]}                '($bracket-apply$ e 1 2)))
+  (pass-if (equal? '{e[1 . 2]}              '($bracket-apply$ e 1 . 2))))
-- 
1.7.10.4

Re: [PATCH] Implement SRFI-105 curly infix expressions

[Mark H Weaver]

[-- Attachment #1: Type: text/plain, Size: 914 bytes --]

Hello all,

Here's an improved version of the SRFI-105 patch for Guile 2.0.  It
incorporates the recent name change 'nfx' --> '$nfx$', has an improved
test suite, and now correctly handles the case where 'curly-infix' is
enabled but the 'square-brackets' read option is disabled.

This patch assumes that the following patch set (per-port read options
and reader directives) has already been applied:

  http://lists.gnu.org/archive/html/guile-devel/2012-10/msg00056.html

Note that in the interests of backward compatibility, SRFI-105 syntax is
enabled by default, since '{' and '}' are currently considered "extended
alphabetic characters".  It must first be enabled in one of two ways:

* On a per-port basis, when the reader encounters the "#!curly-infix"
  reader directive, e.g. near the top of source files.

* Globally, by evaluating: (read-enable 'curly-infix)

Reviews solicited.

   Thanks,
     Mark



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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[-- Type: text/x-diff, Size: 29250 bytes --]

From 4102fbbd852d2f36e13f0c7f10dbac2017552bff Mon Sep 17 00:00:00 2001
From: Mark H Weaver <mhw@netris.org>
Date: Sun, 14 Oct 2012 04:09:01 -0400
Subject: [PATCH] Implement SRFI-105 curly infix expressions.

* libguile/private-options.h: Add SCM_CURLY_INFIX_P macro, and increment
  SCM_N_READ_OPTIONS.

* libguile/read.c (scm_read_opts): Add curly-infix reader option.
  (scm_t_read_opts): Add curly_infix_p field.
  (init_read_options): Initialize new curly_infix_p field.
  (CHAR_IS_DELIMITER): Add '{', '}', '[', and ']' as delimiters if
  curly_infix_p is set.

  (set_per_port_curly_infix_p): New internal static function.

  (scm_read_shebang): Handle '#!curly-infix' reader directive.

  (scm_read, scm_read_keyword, scm_read_vector, scm_read_bytevector):
  Pass new 'neoteric_p' argument to subroutines where needed.

  (scm_read_expression_1): New internal static function, which contains
  the code that was previously in 'scm_read_expression'.  Handle curly
  braces when curly_infix_p is set.  Pass new 'neoteric_p' argument to
  subroutines where needed.

  (scm_read_expression): Add 'neoteric_p' argument.  New function body
  to handle neoteric expressions where appropriate.

  (scm_read_sexp): Add 'neoteric_p' argument.  Handle curly infix
  expressions, converting them to normal s-expressions.

  (flush_ws, scm_read_commented_expression, scm_read_sharp,
  scm_read_quote, scm_read_syntax): Add 'neoteric_p' argument.
  Pass new 'neoteric_p' argument to subroutines where needed.

* doc/ref/srfi-modules.texi (SRFI-105): Add stub doc for SRFI-105.

* doc/ref/api-evaluation.texi (Scheme Read): Add documentation for the
  'curly-infix' read option and the '#!curly-infix' reader directive.

* doc/ref/api-options.texi (Runtime Options): Add 'curly-infix' to the
  list of read options.

* test-suite/Makefile.am: Add tests/srfi-105.test.

* test-suite/tests/srfi-105.test: New file.
---
 doc/ref/api-evaluation.texi    |   10 +-
 doc/ref/api-options.texi       |    1 +
 doc/ref/srfi-modules.texi      |   14 +++
 libguile/private-options.h     |    3 +-
 libguile/read.c                |  231 +++++++++++++++++++++++++++++++---------
 test-suite/Makefile.am         |    1 +
 test-suite/tests/srfi-105.test |   76 +++++++++++++
 7 files changed, 282 insertions(+), 54 deletions(-)
 create mode 100644 test-suite/tests/srfi-105.test

diff --git a/doc/ref/api-evaluation.texi b/doc/ref/api-evaluation.texi
index 9eccb39..245d4e0 100644
--- a/doc/ref/api-evaluation.texi
+++ b/doc/ref/api-evaluation.texi
@@ -338,13 +338,15 @@ r6rs-hex-escapes  no    Use R6RS variable-length character and string hex escape
 square-brackets   yes   Treat `[' and `]' as parentheses, for R6RS compatibility.
 hungry-eol-escapes no   In strings, consume leading whitespace after an
                         escaped end-of-line.
+curly-infix       no    Support SRFI-105 curly infix expressions.
 @end smalllisp
 
 Note that Guile also includes a preliminary mechanism for overriding
-read options on a per-port basis.  Currently, the only read option that
-is overridden in this way is the @code{case-insensitive} option, which
-is set or unset when the reader encounters the special directives
-@code{#!fold-case} or @code{#!no-fold-case}.  There is currently no
+read options on a per-port basis.  The only read options that can
+currently be overridden in this way are the @code{case-insensitive} and
+@code{curly-infix} options, which are set (or unset) when the reader
+encounters the special directives @code{#!fold-case},
+@code{#!no-fold-case}, or @code{#!curly-infix}.  There is currently no
 other way to access or set these per-port read options.
 
 The boolean options may be toggled with @code{read-enable} and
diff --git a/doc/ref/api-options.texi b/doc/ref/api-options.texi
index f635978..1734318 100644
--- a/doc/ref/api-options.texi
+++ b/doc/ref/api-options.texi
@@ -390,6 +390,7 @@ r6rs-hex-escapes  no    Use R6RS variable-length character and string hex escape
 square-brackets   yes   Treat `[' and `]' as parentheses, for R6RS compatibility.
 hungry-eol-escapes no   In strings, consume leading whitespace after an
                         escaped end-of-line.
+curly-infix       no    Support SRFI-105 curly infix expressions.
 scheme@@(guile-user) [1]> (read-enable 'case-insensitive)
 $2 = (square-brackets keywords #f case-insensitive positions)
 scheme@@(guile-user) [1]> ,q
diff --git a/doc/ref/srfi-modules.texi b/doc/ref/srfi-modules.texi
index ba701a2..bf7b3f2 100644
--- a/doc/ref/srfi-modules.texi
+++ b/doc/ref/srfi-modules.texi
@@ -54,6 +54,7 @@ get the relevant SRFI documents from the SRFI home page
 * SRFI-69::                     Basic hash tables.
 * SRFI-88::                     Keyword objects.
 * SRFI-98::                     Accessing environment variables.
+* SRFI-105::                    Curly infix expressions.
 @end menu
 
 
@@ -4469,6 +4470,19 @@ Returns the names and values of all the environment variables as an
 association list in which both the keys and the values are strings.
 @end deffn
 
+@node SRFI-105
+@subsection SRFI-105 Curly infix expressions.
+@cindex SRFI-105
+@cindex curly infix expressions
+@cindex curly-infix
+
+Guile's built-in reader includes support for SRFI-105 curly infix
+expressions.  To enable curly infix expressions, place the reader
+directive @code{#!curly-infix} near the top of each source file.  To
+globally enable curly infix expressions in Guile's reader, set the
+@code{curly-infix} reader option.  For more information on reader
+options, @xref{Scheme Read}.
+
 @c srfi-modules.texi ends here
 
 @c Local Variables:
diff --git a/libguile/private-options.h b/libguile/private-options.h
index 9d2d43c..ed0f314 100644
--- a/libguile/private-options.h
+++ b/libguile/private-options.h
@@ -67,7 +67,8 @@ SCM_INTERNAL scm_t_option scm_read_opts[];
 #define SCM_R6RS_ESCAPES_P     scm_read_opts[4].val
 #define SCM_SQUARE_BRACKETS_P  scm_read_opts[5].val
 #define SCM_HUNGRY_EOL_ESCAPES_P scm_read_opts[6].val
+#define SCM_CURLY_INFIX_P      scm_read_opts[7].val
 
-#define SCM_N_READ_OPTIONS 6
+#define SCM_N_READ_OPTIONS 7
 
 #endif  /* PRIVATE_OPTIONS */ 
diff --git a/libguile/read.c b/libguile/read.c
index da51a05..5a3cdb4 100644
--- a/libguile/read.c
+++ b/libguile/read.c
@@ -63,6 +63,10 @@ SCM_SYMBOL (scm_keyword_prefix, "prefix");
 SCM_SYMBOL (scm_keyword_postfix, "postfix");
 SCM_SYMBOL (sym_nil, "nil");
 
+/* SRFI-105 curly infix expression support */
+SCM_SYMBOL (sym_nfx, "$nfx$");
+SCM_SYMBOL (sym_bracket_apply, "$bracket-apply$");
+
 scm_t_option scm_read_opts[] = {
   { SCM_OPTION_BOOLEAN, "copy", 0,
     "Copy source code expressions." },
@@ -78,6 +82,8 @@ scm_t_option scm_read_opts[] = {
     "Treat `[' and `]' as parentheses, for R6RS compatibility."},
   { SCM_OPTION_BOOLEAN, "hungry-eol-escapes", 0,
     "In strings, consume leading whitespace after an escaped end-of-line."},
+  { SCM_OPTION_BOOLEAN, "curly-infix", 0,
+    "Support SRFI-105 curly infix expressions."},
   { 0, },
 };
 
@@ -96,6 +102,7 @@ typedef struct {
   char r6rs_escapes_p;
   char square_brackets_p;
   char hungry_eol_escapes_p;
+  char curly_infix_p;
 } scm_t_read_opts;
 
 /*
@@ -129,7 +136,8 @@ SCM_SYMBOL (sym_read_option_overrides, "%read-option-overrides%");
 #define OVERRIDE_SHIFT_R6RS_ESCAPES_P         8
 #define OVERRIDE_SHIFT_SQUARE_BRACKETS_P     10
 #define OVERRIDE_SHIFT_HUNGRY_EOL_ESCAPES_P  12
-#define OVERRIDES_SHIFT_END                  14
+#define OVERRIDE_SHIFT_CURLY_INFIX_P         14
+#define OVERRIDES_SHIFT_END                  16
 
 #define OVERRIDES_ALL_DEFAULTS  ((1UL << OVERRIDES_SHIFT_END) - 1)
 #define OVERRIDES_MAX_VALUE     OVERRIDES_ALL_DEFAULTS
@@ -168,6 +176,15 @@ set_per_port_case_insensitive_p (SCM port, scm_t_read_opts *opts, int value)
   set_per_port_read_option (port, OVERRIDE_SHIFT_CASE_INSENSITIVE_P, value);
 }
 
+/* Set curly_infix_p on a per-port basis. */
+static void
+set_per_port_curly_infix_p (SCM port, scm_t_read_opts *opts, int value)
+{
+  value = !!value;
+  opts->curly_infix_p = value;
+  set_per_port_read_option (port, OVERRIDE_SHIFT_CURLY_INFIX_P, value);
+}
+
 /* Initialize the internal read options structure from the global and
    per-port read options. */
 static void
@@ -214,6 +231,7 @@ init_read_options (SCM port, scm_t_read_opts *opts)
   RESOLVE_BOOLEAN_OPTION(R6RS_ESCAPES_P,       r6rs_escapes_p);
   RESOLVE_BOOLEAN_OPTION(SQUARE_BRACKETS_P,    square_brackets_p);
   RESOLVE_BOOLEAN_OPTION(HUNGRY_EOL_ESCAPES_P, hungry_eol_escapes_p);
+  RESOLVE_BOOLEAN_OPTION(CURLY_INFIX_P,        curly_infix_p);
 
 #undef RESOLVE_BOOLEAN_OPTION
 }
@@ -330,7 +348,9 @@ scm_i_read_hash_procedures_set_x (SCM value)
 
 #define CHAR_IS_DELIMITER(c)                                    \
   (CHAR_IS_R5RS_DELIMITER (c)                                   \
-   || (opts->square_brackets_p && ((c) == ']' || (c) == '[')))
+   || (((c) == ']' || (c) == '[') && (opts->square_brackets_p   \
+                                      || opts->curly_infix_p))  \
+   || (((c) == '}' || (c) == '{') && opts->curly_infix_p))
 
 /* Exponent markers, as defined in section 7.1.1 of R5RS, ``Lexical
    Structure''.  */
@@ -341,7 +361,8 @@ scm_i_read_hash_procedures_set_x (SCM value)
 /* Read an SCSH block comment.  */
 static SCM scm_read_scsh_block_comment (scm_t_wchar, SCM);
 static SCM scm_read_r6rs_block_comment (scm_t_wchar, SCM);
-static SCM scm_read_commented_expression (scm_t_wchar, SCM, scm_t_read_opts *);
+static SCM scm_read_commented_expression (scm_t_wchar, SCM,
+                                          scm_t_read_opts *, int);
 static SCM scm_read_shebang (scm_t_wchar, SCM, scm_t_read_opts *);
 static SCM scm_get_hash_procedure (int);
 
@@ -427,7 +448,7 @@ read_complete_token (SCM port, scm_t_read_opts *opts,
 /* Skip whitespace from PORT and return the first non-whitespace character
    read.  Raise an error on end-of-file.  */
 static int
-flush_ws (SCM port, scm_t_read_opts *opts, const char *eoferr)
+flush_ws (SCM port, scm_t_read_opts *opts, int neoteric_p, const char *eoferr)
 {
   scm_t_wchar c;
   while (1)
@@ -467,7 +488,7 @@ flush_ws (SCM port, scm_t_read_opts *opts, const char *eoferr)
 	    scm_read_shebang (c, port, opts);
 	    break;
 	  case ';':
-	    scm_read_commented_expression (c, port, opts);
+	    scm_read_commented_expression (c, port, opts, neoteric_p);
 	    break;
 	  case '|':
 	    if (scm_is_false (scm_get_hash_procedure (c)))
@@ -498,9 +519,10 @@ flush_ws (SCM port, scm_t_read_opts *opts, const char *eoferr)
 \f
 /* Token readers.  */
 
-static SCM scm_read_expression (SCM port, scm_t_read_opts *opts);
+static SCM scm_read_expression (SCM port, scm_t_read_opts *opts,
+                                int neoteric_p);
 static SCM scm_read_sharp (int chr, SCM port, scm_t_read_opts *opts,
-                           long line, int column);
+                           int neoteric_p, long line, int column);
 
 
 static SCM
@@ -513,31 +535,35 @@ maybe_annotate_source (SCM x, SCM port, scm_t_read_opts *opts,
 }
 
 static SCM
-scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
+scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts, int neoteric_p)
 #define FUNC_NAME "scm_i_lreadparen"
 {
   int c;
   SCM tmp, tl, ans = SCM_EOL;
-  const int terminating_char = ((chr == '[') ? ']' : ')');
+  const int curly_infix_p = (chr == '{');
+  const int terminating_char = ((chr == '{') ? '}'
+                                : ((chr == '[') ? ']'
+                                   : ')'));
 
   /* Need to capture line and column numbers here. */
   long line = SCM_LINUM (port);
   int column = SCM_COL (port) - 1;
 
-  c = flush_ws (port, opts, FUNC_NAME);
+  c = flush_ws (port, opts, neoteric_p, FUNC_NAME);
   if (terminating_char == c)
     return SCM_EOL;
 
   scm_ungetc (c, port);
-  tmp = scm_read_expression (port, opts);
+  tmp = scm_read_expression (port, opts, neoteric_p);
 
   /* Note that it is possible for scm_read_expression to return
      scm_sym_dot, but not as part of a dotted pair: as in #{.}#.  So
      check that it's a real dot by checking `c'.  */
   if (c == '.' && scm_is_eq (scm_sym_dot, tmp))
     {
-      ans = scm_read_expression (port, opts);
-      if (terminating_char != (c = flush_ws (port, opts, FUNC_NAME)))
+      ans = scm_read_expression (port, opts, neoteric_p);
+      if (terminating_char != (c = flush_ws (port, opts, neoteric_p,
+                                             FUNC_NAME)))
 	scm_i_input_error (FUNC_NAME, port, "missing close paren",
 			   SCM_EOL);
       return ans;
@@ -546,28 +572,30 @@ scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
   /* Build the head of the list structure. */
   ans = tl = scm_cons (tmp, SCM_EOL);
 
-  while (terminating_char != (c = flush_ws (port, opts, FUNC_NAME)))
+  while (terminating_char != (c = flush_ws (port, opts, neoteric_p,
+                                            FUNC_NAME)))
     {
       SCM new_tail;
 
-      if (c == ')' || (opts->square_brackets_p && c == ']'))
+      if (c == ')' || (opts->square_brackets_p && c == ']')
+          || (opts->curly_infix_p && (c == '}' || c == ']')))
         scm_i_input_error (FUNC_NAME, port,
                            "in pair: mismatched close paren: ~A",
                            scm_list_1 (SCM_MAKE_CHAR (c)));
 
       scm_ungetc (c, port);
-      tmp = scm_read_expression (port, opts);
+      tmp = scm_read_expression (port, opts, neoteric_p);
 
       /* See above note about scm_sym_dot.  */
       if (c == '.' && scm_is_eq (scm_sym_dot, tmp))
 	{
-	  SCM_SETCDR (tl, scm_read_expression (port, opts));
+	  SCM_SETCDR (tl, scm_read_expression (port, opts, neoteric_p));
 
-	  c = flush_ws (port, opts, FUNC_NAME);
+	  c = flush_ws (port, opts, neoteric_p, FUNC_NAME);
 	  if (terminating_char != c)
 	    scm_i_input_error (FUNC_NAME, port,
 			       "in pair: missing close paren", SCM_EOL);
-	  goto exit;
+	  break;
 	}
 
       new_tail = scm_cons (tmp, SCM_EOL);
@@ -575,8 +603,51 @@ scm_read_sexp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
       tl = new_tail;
     }
 
- exit:
-  return maybe_annotate_source (ans, port, opts, line, column);
+  if (curly_infix_p)
+    {
+      int len = scm_ilength (ans);
+
+      if (len == 1)
+        ans = scm_car (ans);
+      else if (len == 2)
+        ;  /* Leave the list unchanged */
+      else if (len >= 3 && (len & 1))
+        {
+          SCM op = scm_cadr (ans);
+
+          /* Verify that all infix operators are 'equal?' */
+          for (tl = scm_cdddr (ans); ; tl = scm_cddr (tl))
+            {
+              if (scm_is_null (tl))
+                {
+                  tl = ans;
+
+                  /* Convert simple curly-infix list to prefix */
+                  while (scm_is_pair (scm_cdr (tl)))
+                    {
+                      tmp = scm_cddr (tl);
+                      SCM_SETCDR (tl, tmp);
+                      tl = tmp;
+                    }
+                  ans = scm_cons (op, ans);
+                  break;
+                }
+              else if (scm_is_false (scm_equal_p (op, scm_car (tl))))
+                {
+                  /* Mixed curly-infix list */
+                  ans = scm_cons (sym_nfx, ans);
+                  break;
+                }
+            }
+        }
+      else
+        ans = scm_cons (sym_nfx, ans);  /* Mixed curly-infix list */
+    }
+
+  if (SCM_NIMP (ans))
+    return maybe_annotate_source (ans, port, opts, line, column);
+  else
+    return ans;
 }
 #undef FUNC_NAME
 
@@ -875,7 +946,7 @@ scm_read_number_and_radix (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
 #undef FUNC_NAME
 
 static SCM
-scm_read_quote (int chr, SCM port, scm_t_read_opts *opts)
+scm_read_quote (int chr, SCM port, scm_t_read_opts *opts, int neoteric_p)
 {
   SCM p;
   long line = SCM_LINUM (port);
@@ -912,7 +983,7 @@ scm_read_quote (int chr, SCM port, scm_t_read_opts *opts)
       abort ();
     }
 
-  p = scm_cons2 (p, scm_read_expression (port, opts), SCM_EOL);
+  p = scm_cons2 (p, scm_read_expression (port, opts, neoteric_p), SCM_EOL);
   return maybe_annotate_source (p, port, opts, line, column);
 }
 
@@ -922,7 +993,7 @@ SCM_SYMBOL (sym_unsyntax, "unsyntax");
 SCM_SYMBOL (sym_unsyntax_splicing, "unsyntax-splicing");
 
 static SCM
-scm_read_syntax (int chr, SCM port, scm_t_read_opts *opts)
+scm_read_syntax (int chr, SCM port, scm_t_read_opts *opts, int neoteric_p)
 {
   SCM p;
   long line = SCM_LINUM (port);
@@ -959,7 +1030,7 @@ scm_read_syntax (int chr, SCM port, scm_t_read_opts *opts)
       abort ();
     }
 
-  p = scm_cons2 (p, scm_read_expression (port, opts), SCM_EOL);
+  p = scm_cons2 (p, scm_read_expression (port, opts, neoteric_p), SCM_EOL);
   return maybe_annotate_source (p, port, opts, line, column);
 }
 
@@ -1128,7 +1199,7 @@ scm_read_keyword (int chr, SCM port, scm_t_read_opts *opts)
      to adapt to the delimiters currently valid of symbols.
 
      XXX: This implementation allows sloppy syntaxes like `#:  key'.  */
-  symbol = scm_read_expression (port, opts);
+  symbol = scm_read_expression (port, opts, 0);
   if (!scm_is_symbol (symbol))
     scm_i_input_error ("scm_read_keyword", port,
 		       "keyword prefix `~a' not followed by a symbol: ~s",
@@ -1145,8 +1216,9 @@ scm_read_vector (int chr, SCM port, scm_t_read_opts *opts,
      guarantee that it's going to do what we want.  After all, this is an
      implementation detail of `scm_read_vector ()', not a desirable
      property.  */
-  return maybe_annotate_source (scm_vector (scm_read_sexp (chr, port, opts)),
-                                port, opts, line, column);
+  return maybe_annotate_source
+    (scm_vector (scm_read_sexp (chr, port, opts, 0)),
+     port, opts, line, column);
 }
 
 static SCM
@@ -1184,7 +1256,7 @@ scm_read_bytevector (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
     goto syntax;
 
   return maybe_annotate_source
-    (scm_u8_list_to_bytevector (scm_read_sexp (chr, port, opts)),
+    (scm_u8_list_to_bytevector (scm_read_sexp (chr, port, opts, 0)),
      port, opts, line, column);
 
  syntax:
@@ -1267,6 +1339,8 @@ scm_read_shebang (scm_t_wchar chr, SCM port, scm_t_read_opts *opts)
             set_per_port_case_insensitive_p (port, opts, 1);
           else if (0 == strcmp ("no-fold-case", name))
             set_per_port_case_insensitive_p (port, opts, 0);
+          else if (0 == strcmp ("curly-infix", name))
+            set_per_port_curly_infix_p (port, opts, 1);
           else
             break;
 
@@ -1318,16 +1392,16 @@ scm_read_r6rs_block_comment (scm_t_wchar chr, SCM port)
 
 static SCM
 scm_read_commented_expression (scm_t_wchar chr, SCM port,
-                               scm_t_read_opts *opts)
+                               scm_t_read_opts *opts, int neoteric_p)
 {
   scm_t_wchar c;
   
-  c = flush_ws (port, opts, (char *) NULL);
+  c = flush_ws (port, opts, neoteric_p, (char *) NULL);
   if (EOF == c)
     scm_i_input_error ("read_commented_expression", port,
                        "no expression after #; comment", SCM_EOL);
   scm_ungetc (c, port);
-  scm_read_expression (port, opts);
+  scm_read_expression (port, opts, neoteric_p);
   return SCM_UNSPECIFIED;
 }
 
@@ -1456,7 +1530,7 @@ scm_read_sharp_extension (int chr, SCM port, scm_t_read_opts *opts)
    among the above token readers.   */
 static SCM
 scm_read_sharp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
-                long line, int column)
+                int neoteric_p, long line, int column)
 #define FUNC_NAME "scm_lreadr"
 {
   SCM result;
@@ -1531,11 +1605,11 @@ scm_read_sharp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
     case '!':
       return (scm_read_shebang (chr, port, opts));
     case ';':
-      return (scm_read_commented_expression (chr, port, opts));
+      return (scm_read_commented_expression (chr, port, opts, neoteric_p));
     case '`':
     case '\'':
     case ',':
-      return (scm_read_syntax (chr, port, opts));
+      return (scm_read_syntax (chr, port, opts, neoteric_p));
     case 'n':
       return (scm_read_nil (chr, port, opts));
     default:
@@ -1563,8 +1637,8 @@ scm_read_sharp (scm_t_wchar chr, SCM port, scm_t_read_opts *opts,
 #undef FUNC_NAME
 
 static SCM
-scm_read_expression (SCM port, scm_t_read_opts *opts)
-#define FUNC_NAME "scm_read_expression"
+scm_read_expression_1 (SCM port, scm_t_read_opts *opts, int neoteric_p)
+#define FUNC_NAME "scm_read_expression_1"
 {
   while (1)
     {
@@ -1580,23 +1654,42 @@ scm_read_expression (SCM port, scm_t_read_opts *opts)
 	case ';':
 	  (void) scm_read_semicolon_comment (chr, port);
 	  break;
+        case '{':
+          if (opts->curly_infix_p)
+            return (scm_read_sexp (chr, port, opts, 1));
+          else
+            return (scm_read_mixed_case_symbol (chr, port, opts));
+        case '}':
+          if (opts->curly_infix_p)
+            scm_i_input_error (FUNC_NAME, port, "unexpected \"}\"", SCM_EOL);
+          else
+            return (scm_read_mixed_case_symbol (chr, port, opts));
 	case '[':
-          if (!opts->square_brackets_p)
+          if (opts->square_brackets_p)
+            return (scm_read_sexp (chr, port, opts, neoteric_p));
+          else if (opts->curly_infix_p)
+            scm_i_input_error (FUNC_NAME, port, "unexpected \"[\"", SCM_EOL);
+          else
+            return (scm_read_mixed_case_symbol (chr, port, opts));
+	case ']':
+          if (opts->square_brackets_p || opts->curly_infix_p)
+            scm_i_input_error (FUNC_NAME, port, "unexpected \"]\"", SCM_EOL);
+          else
             return (scm_read_mixed_case_symbol (chr, port, opts));
-          /* otherwise fall through */
 	case '(':
-	  return (scm_read_sexp (chr, port, opts));
+	  return (scm_read_sexp (chr, port, opts, neoteric_p));
 	case '"':
 	  return (scm_read_string (chr, port, opts));
 	case '\'':
 	case '`':
 	case ',':
-	  return (scm_read_quote (chr, port, opts));
+	  return (scm_read_quote (chr, port, opts, neoteric_p));
 	case '#':
 	  {
             long line  = SCM_LINUM (port);
             int column = SCM_COL (port) - 1;
-	    SCM result = scm_read_sharp (chr, port, opts, line, column);
+            SCM result = scm_read_sharp (chr, port, opts, neoteric_p,
+                                         line, column);
 	    if (scm_is_eq (result, SCM_UNSPECIFIED))
 	      /* We read a comment or some such.  */
 	      break;
@@ -1606,15 +1699,12 @@ scm_read_expression (SCM port, scm_t_read_opts *opts)
 	case ')':
 	  scm_i_input_error (FUNC_NAME, port, "unexpected \")\"", SCM_EOL);
 	  break;
-	case ']':
-          if (opts->square_brackets_p)
-            scm_i_input_error (FUNC_NAME, port, "unexpected \"]\"", SCM_EOL);
-          /* otherwise fall through */
 	case EOF:
 	  return SCM_EOF_VAL;
 	case ':':
 	  if (opts->keyword_style == KEYWORD_STYLE_PREFIX)
-	    return scm_symbol_to_keyword (scm_read_expression (port, opts));
+	    return scm_symbol_to_keyword
+              (scm_read_expression (port, opts, neoteric_p));
 	  /* Fall through.  */
 
 	default:
@@ -1630,6 +1720,49 @@ scm_read_expression (SCM port, scm_t_read_opts *opts)
 }
 #undef FUNC_NAME
 
+static SCM
+scm_read_expression (SCM port, scm_t_read_opts *opts, int neoteric_p)
+#define FUNC_NAME "scm_read_expression"
+{
+  if (!neoteric_p)
+    return scm_read_expression_1 (port, opts, 0);
+  else
+    {
+      long line = SCM_LINUM (port);
+      int column = SCM_COL (port) - 1;
+      SCM expr = scm_read_expression_1 (port, opts, 1);
+
+      for (;;)
+        {
+          int chr = scm_getc (port);
+
+          if (chr == '(')
+            expr = scm_cons (expr, scm_read_sexp (chr, port, opts, 1));
+          else if (chr == '[')
+            expr = scm_cons (sym_bracket_apply,
+                             scm_cons (expr,
+                                       scm_read_sexp (chr, port, opts, 1)));
+          else if (chr == '{')
+            {
+              SCM arg = scm_read_sexp (chr, port, opts, 1);
+
+              if (scm_is_null (arg))
+                expr = scm_list_1 (expr);
+              else
+                expr = scm_list_2 (expr, arg);
+            }
+          else
+            {
+              scm_ungetc (chr, port);
+              break;
+            }
+          maybe_annotate_source (expr, port, opts, line, column);
+        }
+      return expr;
+    }
+}
+#undef FUNC_NAME
+
 \f
 /* Actual reader.  */
 
@@ -1649,12 +1782,12 @@ SCM_DEFINE (scm_read, "read", 0, 1, 0,
 
   init_read_options (port, &opts);
 
-  c = flush_ws (port, &opts, (char *) NULL);
+  c = flush_ws (port, &opts, 0, (char *) NULL);
   if (EOF == c)
     return SCM_EOF_VAL;
   scm_ungetc (c, port);
 
-  return (scm_read_expression (port, &opts));
+  return (scm_read_expression (port, &opts, 0));
 }
 #undef FUNC_NAME
 
diff --git a/test-suite/Makefile.am b/test-suite/Makefile.am
index 168e799..a843fcd 100644
--- a/test-suite/Makefile.am
+++ b/test-suite/Makefile.am
@@ -136,6 +136,7 @@ SCM_TESTS = tests/00-initial-env.test		\
 	    tests/srfi-67.test			\
 	    tests/srfi-69.test			\
 	    tests/srfi-88.test			\
+	    tests/srfi-105.test			\
 	    tests/srfi-4.test			\
 	    tests/srfi-9.test			\
 	    tests/statprof.test			\
diff --git a/test-suite/tests/srfi-105.test b/test-suite/tests/srfi-105.test
new file mode 100644
index 0000000..a0ed0ee
--- /dev/null
+++ b/test-suite/tests/srfi-105.test
@@ -0,0 +1,76 @@
+;;;; srfi-105.test --- Test suite for Guile's SRFI-105 reader. -*- scheme -*-
+;;;;
+;;;; Copyright (C) 2012 Free Software Foundation, Inc.
+;;;;
+;;;; This library is free software; you can redistribute it and/or
+;;;; modify it under the terms of the GNU Lesser General Public
+;;;; License as published by the Free Software Foundation; either
+;;;; version 3 of the License, or (at your option) any later version.
+;;;;
+;;;; This library is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;;; Lesser General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU Lesser General Public
+;;;; License along with this library; if not, write to the Free Software
+;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+#!curly-infix
+
+(define-module (test-srfi-105)
+  #:use-module (test-suite lib)
+  #:use-module (srfi srfi-1))
+
+(with-test-prefix "curly-infix"
+  (pass-if (equal? '{n <= 5}                '(<= n 5)))
+  (pass-if (equal? '{a + b + c}             '(+ a b c)))
+  (pass-if (equal? '{x ,op y ,op z}         '(,op x y z)))
+  (pass-if (equal? '{a * {b + c}}           '(* a (+ b c))))
+  (pass-if (equal? '{x eqv? `a}             '(eqv? x `a)))
+  (pass-if (equal? '{(- a) / b}             '(/ (- a) b)))
+  (pass-if (equal? '{-(a) / b}              '(/ (- a) b)))
+  (pass-if (equal? '{(f a b) + (g h)}       '(+ (f a b) (g h))))
+  (pass-if (equal? '{f(a b) + g(h)}         '(+ (f a b) (g h))))
+  (pass-if (equal? '{f(g(x))}               '(f (g x))))
+  (pass-if (equal? '{f(g(x) h(x))}          '(f (g x) (h x))))
+  (pass-if (equal? '{ (f (g h(x))) }        '(f (g (h x)))))
+
+  ;; FIXME Unsure about this one!  I've asked for clarification. -mhw
+  (pass-if (equal? '{ (f #(g h(x))) }       '(f #(g h (x)))))
+
+  (pass-if (equal? '{ (f #;g(x) h(x)) }     '(f (h x))))
+
+  (pass-if (equal? '{a + f(b) + x}          '(+ a (f b) x)))
+  (pass-if (equal? '{{a > 0} and {b >= 1}}  '(and (> a 0) (>= b 1))))
+  (pass-if (equal? '{'f(x)}                 '(quote (f x))))
+  ;;(pass-if (equal? '#1=f(#1#)               '#1=(f #1#)))
+  (pass-if (equal? '{length(x) >= 6}        '(>= (length x) 6)))
+
+  (pass-if (equal? '{}                      '()))
+  (pass-if (equal? '{e}                     'e))
+  (pass-if (equal? '{e1 e2}                 '(e1 e2)))
+
+  (pass-if (equal? '{a . t}                 '($nfx$ a . t)))
+  (pass-if (equal? '{a b . t}               '($nfx$ a b . t)))
+  (pass-if (equal? '{a b c . t}             '($nfx$ a b c . t)))
+  (pass-if (equal? '{a b c d . t}           '($nfx$ a b c d . t)))
+  (pass-if (equal? '{a + b +}               '($nfx$ a + b +)))
+  (pass-if (equal? '{a + b + c +}           '($nfx$ a + b + c +)))
+  (pass-if (equal? '{q + r * s}             '($nfx$ q + r * s)))
+  ;;(pass-if (equal? '#1={a + . #1#}          '($nfx$ . #1=(a + . #1#))))
+
+  (pass-if (equal? '{e()}                   '(e)))
+  (pass-if (equal? '{e{}}                   '(e)))
+  (pass-if (equal? '{e(1)}                  '(e 1)))
+  (pass-if (equal? '{e{1}}                  '(e 1)))
+  (pass-if (equal? '{e(1 2)}                '(e 1 2)))
+  (pass-if (equal? '{e{1 2}}                '(e (1 2))))
+  (pass-if (equal? '{f{n - 1}}              '(f (- n 1))))
+  (pass-if (equal? '{f{n - 1}(x)}           '((f (- n 1)) x)))
+  (pass-if (equal? '{g{- x}}                '(g (- x))))
+  (pass-if (equal? '{( . e)}                'e))
+
+  (pass-if (equal? '{e[]}                   '($bracket-apply$ e)))
+  (pass-if (equal? '{e[1 2]}                '($bracket-apply$ e 1 2)))
+  (pass-if (equal? '{e[1 . 2]}              '($bracket-apply$ e 1 . 2))))
-- 
1.7.10.4

Re: [PATCH] Implement SRFI-105 curly infix expressions.

[Ludovic Courtès]

Hi!

My understanding was that the sweet-expressions folks already had
something, no?

And there as also this preliminary patch:

  http://lists.gnu.org/archive/html/guile-devel/2012-03/msg00129.html

What about applying first, then one above, then anything beyond?

Ludo’.

Re: [PATCH] Implement SRFI-105 curly infix expressions.

[Mark H Weaver]

ludo@gnu.org (Ludovic Courtès) writes:
> My understanding was that the sweet-expressions folks already had
> something, no?

The implementation they have (which they call a "demo") reimplements the
entire reader from scratch.  There are several problems with this, the
worst of which is that it strongly discourages anyone from using the
syntax in code that they'd like to deploy.  You can't simply publish a
module with '#!curly-infix' at the top and have people use it.  You have
to ask them to install the sweet-expressions implementation first, and
then ask them to somehow arrange for your code to be read using the
special reader.

> And there as also this preliminary patch:
>
>   http://lists.gnu.org/archive/html/guile-devel/2012-03/msg00129.html
>
> What about applying first, then one above, then anything beyond?

With respect to nalaginrut, that patch was only the beginning, and was
never turned into a full implementation.  I have a fully-functional
patch that implements the full spec, complete with documentation, test
suite, and everything needed to enable people to easily use and deploy
curly-infix in their programs.

     Mark

Re: [PATCH] Implement SRFI-105 curly infix expressions.

[nalaginrut]

On Tue, 2012-10-16 at 16:38 -0400, Mark H Weaver wrote:
> ludo@gnu.org (Ludovic Courtès) writes:
> > My understanding was that the sweet-expressions folks already had
> > something, no?
> 
> The implementation they have (which they call a "demo") reimplements the
> entire reader from scratch.  There are several problems with this, the
> worst of which is that it strongly discourages anyone from using the
> syntax in code that they'd like to deploy.  

Yes, that's true! An integrated sweet-expression reader would be better.
My modified implementation was a multi-language extension one. But now
things has changed, sweet-expression became SRFI-105, so we ought to
make it more seriously.


> You can't simply publish a
> module with '#!curly-infix' at the top and have people use it.  You have
> to ask them to install the sweet-expressions implementation first, and
> then ask them to somehow arrange for your code to be read using the
> special reader.
> 

> > And there as also this preliminary patch:
> >
> >   http://lists.gnu.org/archive/html/guile-devel/2012-03/msg00129.html
> >
> > What about applying first, then one above, then anything beyond?
> 

> With respect to nalaginrut, that patch was only the beginning, and was
> never turned into a full implementation.  I have a fully-functional
> patch that implements the full spec, complete with documentation, test
> suite, and everything needed to enable people to easily use and deploy
> curly-infix in their programs.
> 

Well, I just noticed there's an item "make curly brace delimiter" on
Mark's TODO list. And I did it at the volley. 
There's no SRFI-105 at that time, so I thought an easy implementation
would be enough.

>      Mark
> 

Re: [PATCH] Implement SRFI-105 curly infix expressions.

[Ludovic Courtès]

Hi,

Mark H Weaver <mhw@netris.org> skribis:

> ludo@gnu.org (Ludovic Courtès) writes:
>> My understanding was that the sweet-expressions folks already had
>> something, no?
>
> The implementation they have (which they call a "demo") reimplements the
> entire reader from scratch.  There are several problems with this, the
> worst of which is that it strongly discourages anyone from using the
> syntax in code that they'd like to deploy.  You can't simply publish a
> module with '#!curly-infix' at the top and have people use it.  You have
> to ask them to install the sweet-expressions implementation first, and
> then ask them to somehow arrange for your code to be read using the
> special reader.

Would it help if it were distributed as part of Guile?  That’s something
we could do when the implementation is considered reasonably stable.

Then the current read.c would just need to be extended to dispatch the
#! thing.

WDYT?

(I have nothing against your approach either, but I like the idea of
less work for us, and less C.  ;-))

Thanks,
Ludo’.

Re: [PATCH] Implement SRFI-105 curly infix expressions.

[Mark H Weaver]

ludo@gnu.org (Ludovic Courtès) writes:

> Mark H Weaver <mhw@netris.org> skribis:
>
>> ludo@gnu.org (Ludovic Courtès) writes:
>>> My understanding was that the sweet-expressions folks already had
>>> something, no?
>>
>> The implementation they have (which they call a "demo") reimplements the
>> entire reader from scratch.  There are several problems with this, the
>> worst of which is that it strongly discourages anyone from using the
>> syntax in code that they'd like to deploy.  You can't simply publish a
>> module with '#!curly-infix' at the top and have people use it.  You have
>> to ask them to install the sweet-expressions implementation first, and
>> then ask them to somehow arrange for your code to be read using the
>> special reader.
>
> Would it help if it were distributed as part of Guile?  That’s something
> we could do when the implementation is considered reasonably stable.

That wouldn't work, because #!curly-infix (like any other reader
directive) can appear anywhere that comments are permitted, at any depth
within an s-expr, and must affect all tokens that follow until the end
of the file.

Even if we somehow figured out a way around that problem, the other
problem is that it would require us to maintain two almost identical
readers that implement all of the functionality our reader supports
(e.g. arrays, source properties, read-hash-extend, all of our other read
options, etc), and keep these two implementations in sync with each
other.

   Regards,
     Mark