Patch for ice-9/format.scm (removes arbitrary ~{...~} iteration limit)

Patch for ice-9/format.scm (removes arbitrary ~{...~} iteration limit)

[Matthias Koeppe]

Today I tried to format a long list of elements using the format "~{"
directive.  To my surprise, the list was cut off after the 100th
element.  

I am sending a testcase for Guile's test suite and a patch that fixes
the problem.  The patch is against the stable branch, where it should
be applied in addition to the CVS HEAD.


2004-05-25  Matthias Koeppe  <mkoeppe@mail.math.uni-magdeburg.de>

	* format.scm (format): Remove the arbitrary limit of 100 iterations
	for the ~{...~} control structure.


Index: ice-9/format.scm
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/ice-9/format.scm,v
retrieving revision 1.11.2.2
diff -u -p -r1.11.2.2 format.scm
--- ice-9/format.scm	13 Jan 2004 16:56:11 -0000	1.11.2.2
+++ ice-9/format.scm	25 May 2004 14:17:06 -0000
@@ -614,8 +614,7 @@
 	       (case modifier
 		 ((colon)
 		  (if (not max-iterations) (set! max-iterations 1)))
-		 ((colon-at at) (format:error "illegal modifier"))
-		 (else (if (not max-iterations) (set! max-iterations 100))))
+		 ((colon-at at) (format:error "illegal modifier")))
 	       (if (not (null? params))
 		   (format:error "no parameters allowed in ~~}"))
 	       (if (zero? iteration-nest)
@@ -637,7 +636,8 @@
 					    (list-tail args arg-pos))))
 			     (i 0 (+ i 1)))
 			    ((or (>= arg-pos args-len)
-				 (>= i max-iterations))))))
+				 (and max-iterations
+				      (>= i max-iterations)))))))
 		     ((sublists)
 		      (let ((args (next-arg))
 			    (args-len 0))
@@ -646,7 +646,8 @@
 			(set! args-len (length args))
 			(do ((arg-pos 0 (+ arg-pos 1)))
 			    ((or (>= arg-pos args-len)
-				 (>= arg-pos max-iterations)))
+				 (and max-iterations
+				      (>= arg-pos max-iterations))))
 			  (let ((sublist (list-ref args arg-pos)))
 			    (if (not (list? sublist))
 				(format:error
@@ -663,7 +664,8 @@
 						   args arg-pos))))
 				   (i 0 (+ i 1)))
 				  ((or (>= arg-pos args-len)
-				       (>= i max-iterations))
+				       (and max-iterations
+					    (>= i max-iterations)))
 				   arg-pos))))
 			(add-arg-pos usedup-args)))
 		     ((rest-sublists)
@@ -672,7 +674,8 @@
 			     (usedup-args
 			      (do ((arg-pos 0 (+ arg-pos 1)))
 				  ((or (>= arg-pos args-len)
-				       (>= arg-pos max-iterations))
+				       (and max-iterations
+					    (>= arg-pos max-iterations)))
 				   arg-pos)
 				(let ((sublist (list-ref args arg-pos)))
 				  (if (not (list? sublist))
Index: test-suite/tests/format.test
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/test-suite/tests/format.test,v
retrieving revision 1.1
diff -u -p -r1.1 format.test
--- test-suite/tests/format.test	16 Jun 2001 20:11:39 -0000	1.1
+++ test-suite/tests/format.test	25 May 2004 14:17:06 -0000
@@ -1,7 +1,7 @@
 ;;;; format.test --- test suite for Guile's CL-ish format  -*- scheme -*-
 ;;;; Matthias Koeppe <mkoeppe@mail.math.uni-magdeburg.de> --- June 2001
 ;;;;
-;;;; 	Copyright (C) 2001 Free Software Foundation, Inc.
+;;;; 	Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
 ;;;;
 ;;;; This program is free software; you can redistribute it and/or modify
 ;;;; it under the terms of the GNU General Public License as published by
@@ -36,4 +36,10 @@
 		(format #t "~&abc")
 		(format #f "~&")	; shall have no effect
 		(format #t "~&~&")))
-	    "xyz\nabc\n")))
+	    "xyz\nabc\n"))
+  (pass-if "format ~F (format-out-substr) maintains the column correctly"
+	   (= (string-length (format "~@F~20T" 1)) 20)))
+
+(with-test-prefix "format control flow"
+  (pass-if "format ~{ has no arbitrary iteration limit"
+	   (= (string-length (format "~{~a~}" (make-list 200 #\b))) 200)))
\ No newline at end of file

-- 
Matthias Koeppe -- http://www.math.uni-magdeburg.de/~mkoeppe


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Re: Patch for ice-9/format.scm (removes arbitrary ~{...~} iteration limit)

[Kevin Ryde]

Matthias Koeppe <mkoeppe@merkur.math.uni-magdeburg.de> writes:
>
> To my surprise, the list was cut off after the 100th element.

I've been writing some new doco for format (and adding some checks to
my lint program), and noticed this limit too, but didn't know what it
meant.  The common lisp spec doesn't say anything like it as far as I
can tell.

Maybe it was to avoid going into an infinite loop, but there's plenty
of other ways that can happen :), so it's hardly a motivation.

> I am sending a testcase for Guile's test suite and a patch that fixes
> the problem.

Looks likely.


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Re: Patch for ice-9/format.scm (removes arbitrary ~{...~} iteration limit)

[Matthias Koeppe]

Kevin Ryde <user42@zip.com.au> writes:

> Matthias Koeppe <mkoeppe@merkur.math.uni-magdeburg.de> writes:
>>
>> To my surprise, the list was cut off after the 100th element.
>
> I've been writing some new doco for format (and adding some checks to
> my lint program), and noticed this limit too, but didn't know what it
> meant.  The common lisp spec doesn't say anything like it as far as I
> can tell.

Common Lisp definitely does no such truncation.

> Maybe it was to avoid going into an infinite loop, but there's plenty
> of other ways that can happen :), so it's hardly a motivation.
>
>> I am sending a testcase for Guile's test suite and a patch that fixes
>> the problem.
>
> Looks likely.

Kevin, could you commit the patch to CVS then?  I think this should
go into HEAD and the stable branch.

Thanks
-- 
Matthias Koeppe -- http://www.math.uni-magdeburg.de/~mkoeppe


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Re: Patch for ice-9/format.scm (removes arbitrary ~{...~} iteration limit)

[Kevin Ryde]

Matthias Koeppe <mkoeppe@merkur.math.uni-magdeburg.de> writes:
>
> Kevin, could you commit the patch to CVS then?  I think this should
> go into HEAD and the stable branch.

Done.  Thanks.

> +  (pass-if "format ~F (format-out-substr) maintains the column correctly"
> +	   (= (string-length (format "~@F~20T" 1)) 20)))

Marius has applied this to the head previously.  You can argue for it
in the 1.6 if it addresses some bug or misfeature.

> +  (pass-if "format ~{ has no arbitrary iteration limit"
> +	   (= (string-length (format "~{~a~}" (make-list 200 #\b))) 200)))

Tests exercising the other three iteration forms (~{ modifiers) would
be nice, since the code for those is separate.


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Re: Patch for ice-9/format.scm (removes arbitrary ~{...~} iteration limit)

[Matthias Koeppe]

Kevin Ryde <user42@zip.com.au> writes:

> Matthias Koeppe <mkoeppe@merkur.math.uni-magdeburg.de> writes:
>>
>> Kevin, could you commit the patch to CVS then?  I think this should
>> go into HEAD and the stable branch.
>
> Done.  Thanks.

Thanks.

>> +  (pass-if "format ~F (format-out-substr) maintains the column correctly"
>> +	   (= (string-length (format "~@F~20T" 1)) 20)))
>
> Marius has applied this to the head previously.  You can argue for it
> in the 1.6 if it addresses some bug or misfeature.

It did address a bug, but my patch to fix it is already in CVS.  So no
need to fix it in the stable branch.  (There is little point in having
a "stable" and a HEAD test suite, anyway.)

>> +  (pass-if "format ~{ has no arbitrary iteration limit"
>> +	   (= (string-length (format "~{~a~}" (make-list 200 #\b))) 200)))
>
> Tests exercising the other three iteration forms (~{ modifiers) would
> be nice, since the code for those is separate.

All the tests for FORMAT that I have contributed illustrate a bug that
I found.  Of course a whole test suite for FORMAT would be nice, but I
don't have time to work on it.

-- 
Matthias Koeppe -- http://www.math.uni-magdeburg.de/~mkoeppe


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