bug#19814: 24.4; pcase-lambda

bug#19814: 24.4; pcase-lambda

[Leo Liu]

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The attached patch intends to implement pcase-lambda with lambda-list
being a list of positional UPatterns. &rest is supported. Comments?


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diff --git a/lisp/emacs-lisp/lisp-mode.el b/lisp/emacs-lisp/lisp-mode.el
index 868a9578..5d912097 100644
--- a/lisp/emacs-lisp/lisp-mode.el
+++ b/lisp/emacs-lisp/lisp-mode.el
@@ -204,7 +204,7 @@ (pcase-let
                           "defface"))
               (el-tdefs '("defgroup" "deftheme"))
               (el-kw '("while-no-input" "letrec" "pcase" "pcase-exhaustive"
-                       "pcase-let" "pcase-let*" "save-restriction"
+                       "pcase-lambda" "pcase-let" "pcase-let*" "save-restriction"
                        "save-excursion" "save-selected-window"
                        ;; "eval-after-load" "eval-next-after-load"
                        "save-window-excursion" "save-current-buffer"
diff --git a/lisp/emacs-lisp/macroexp.el b/lisp/emacs-lisp/macroexp.el
index 797de9ab..8fe156c4 100644
--- a/lisp/emacs-lisp/macroexp.el
+++ b/lisp/emacs-lisp/macroexp.el
@@ -297,6 +297,16 @@ (defun macroexpand-all (form &optional environment)
 
 ;;; Handy functions to use in macros.
 
+(defun macroexp-parse-body (exps)
+  "Parse EXPS into (DOC DECLARE-FORM INTERACTIVE-FORM . BODY)."
+  `(,(and (stringp (car exps))
+          (pop exps))
+    ,(and (eq (car-safe (car exps)) 'declare)
+          (pop exps))
+    ,(and (eq (car-safe (car exps)) 'interactive)
+          (pop exps))
+    ,@exps))
+
 (defun macroexp-progn (exps)
   "Return an expression equivalent to `(progn ,@EXPS)."
   (if (cdr exps) `(progn ,@exps) (car exps)))
diff --git a/lisp/emacs-lisp/pcase.el b/lisp/emacs-lisp/pcase.el
index b495793b..0c71451b 100644
--- a/lisp/emacs-lisp/pcase.el
+++ b/lisp/emacs-lisp/pcase.el
@@ -164,6 +164,23 @@ (defmacro pcase-exhaustive (exp &rest cases)
      ;; FIXME: Could we add the FILE:LINE data in the error message?
      exp (append cases `((,x (error "No clause matching `%S'" ,x)))))))
 
+;;;###autoload
+(defmacro pcase-lambda (lambda-list &rest body)
+  (declare (doc-string 2) (indent defun))
+  (let ((args (make-symbol "args"))
+        (pats (mapcar (lambda (u)
+                        (unless (eq u '&rest)
+                          (if (eq (car-safe u) '\`) (cadr u) (list '\, u))))
+                      lambda-list))
+        (body (macroexp-parse-body body)))
+    ;; Handle &rest
+    (when (eq nil (car (last pats 2)))
+      (setq pats (append (butlast pats 2) (car (last pats)))))
+    `(lambda (&rest ,args)
+       ,@(remq nil (list (nth 0 body) (nth 1 body) (nth 2 body)))
+       (pcase ,args
+         (,(list '\` pats) . ,(nthcdr 3 body))))))
+
 (defun pcase--let* (bindings body)
   (cond
    ((null bindings) (macroexp-progn body))

bug#19814: 24.4; pcase-lambda

[Stefan Monnier]

> +(defun macroexp-parse-body (exps)
> +  "Parse EXPS into (DOC DECLARE-FORM INTERACTIVE-FORM . BODY)."
> +  `(,(and (stringp (car exps))
> +          (pop exps))
> +    ,(and (eq (car-safe (car exps)) 'declare)
> +          (pop exps))
> +    ,(and (eq (car-safe (car exps)) 'interactive)
> +          (pop exps))
> +    ,@exps))

Maybe it'd be better to just splitting the body into 2 parts:
- "declarations", which would include docstrings, `declare's, and interactive
- code.


        Stefan

bug#19814: 24.4; pcase-lambda

[Leo Liu]

On 2015-02-09 03:18 +0800, Stefan Monnier wrote:
> Maybe it'd be better to just splitting the body into 2 parts:
> - "declarations", which would include docstrings, `declare's, and interactive
> - code.

Coincidentally I have done just that locally :)

(defun macroexp-parse-body (exps)
  "Parse EXPS into ((DOC DECLARE-FORM INTERACTIVE-FORM) . BODY)."
  `((,(and (stringp (car exps))
           (pop exps))
     ,(and (eq (car-safe (car exps)) 'declare)
           (pop exps))
     ,(and (eq (car-safe (car exps)) 'interactive)
           (pop exps)))
    ,@exps))

Leo

bug#19814: 24.4; pcase-lambda

[Leo Liu]

Version: 25.1

bug#19814: 24.4; pcase-lambda

[Stefan Monnier]

>> Maybe it'd be better to just splitting the body into 2 parts:
>> - "declarations", which would include docstrings, `declare's, and interactive
>> - code.
> Coincidentally I have done just that locally :)

> (defun macroexp-parse-body (exps)
>   "Parse EXPS into ((DOC DECLARE-FORM INTERACTIVE-FORM) . BODY)."
>   `((,(and (stringp (car exps))
>            (pop exps))
>      ,(and (eq (car-safe (car exps)) 'declare)
>            (pop exps))
>      ,(and (eq (car-safe (car exps)) 'interactive)
>            (pop exps)))
>     ,@exps))

No, I meant (DECLS . BODY) such that

  (let ((x (macroexp-parse-body body)))
    (append (car x) (cdr x)))

return something `equal' to `body'.




        Stefan

bug#19814: 24.4; pcase-lambda

[Leo Liu]

On 2015-02-09 12:27 +0800, Stefan Monnier wrote:
> No, I meant (DECLS . BODY) such that
>
>   (let ((x (macroexp-parse-body body)))
>     (append (car x) (cdr x)))
>
> return something `equal' to `body'.

Ahh, I see. We can certainly do that.

But isn't the version committed to master slightly more flexible i.e.
one can easily access the individual DOC, DECLARE or INTERACTIVE form?
And if one wants to use the prelude (without the `nil') as a whole it is
just (remq nil (car PARSED-BODY)) away? What do you think?

Leo