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(pcase): New _ syntax in pred/app functions

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The current syntax for functions in `app` and `pred` patterns
allows a shorthand (F ARGS) where the object being matched is
added as an extra last argument.  This is nice for things like
(pred (< 5)) but sometimes the object needs to be at
another position.
Until now you had to use (pred (lambda (x) (memq x my-list)))
or (pred (pcase--flip memq my-list)) in those cases.
So, introduce a new shorthand where `_` can be used to indicate
where the object should be passed: (pred (memq _ my-list))

* lisp/emacs-lisp/pcase.el (pcase--split-pred): Document new syntax
for pred/app functions.
(pcase--funcall): Support new syntax.
(pcase--flip): Declare obsolete.
(pcase--u1, \`): Use `_` instead.
(pcase--split-pred): Adjust accordingly.

* doc/lispref/control.texi (pcase Macro): Document new syntax
for pred/app functions.

* lisp/progmodes/opascal.el (pcase-defmacro):
* lisp/emacs-lisp/seq.el (seq--make-pcase-bindings):
* lisp/emacs-lisp/eieio.el (eieio):
* lisp/emacs-lisp/cl-macs.el (cl-struct, cl-type):
Use _ instead of `pcase--flip`.
(cl--pcase-mutually-exclusive-p): Adjust accordingly.

* lisp/emacs-lisp/map.el (map--pcase-map-elt): Declare obsolete.
(map--make-pcase-bindings): Use `_` instead.
This commit is contained in:
Stefan Monnier 2024-02-11 22:00:44 -05:00
parent 9ebc91795f
commit 806759dc0a
8 changed files with 47 additions and 24 deletions
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15
lisp/emacs-lisp/cl-macs.el
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@ -3344,14 +3344,14 @@ Elements of FIELDS can be of the form (NAME PAT) in which case the
contents of field NAME is matched against PAT, or they can be of
the form NAME which is a shorthand for (NAME NAME)."
(declare (debug (sexp &rest [&or (sexp pcase-PAT) sexp])))
`(and (pred (pcase--flip cl-typep ',type))
`(and (pred (cl-typep _ ',type))
,@(mapcar
(lambda (field)
(let* ((name (if (consp field) (car field) field))
(pat (if (consp field) (cadr field) field)))
`(app ,(if (eq (cl-struct-sequence-type type) 'list)
`(nth ,(cl-struct-slot-offset type name))
`(pcase--flip aref ,(cl-struct-slot-offset type name)))
`(aref _ ,(cl-struct-slot-offset type name)))
,pat)))
fields)))
@ -3368,13 +3368,13 @@ the form NAME which is a shorthand for (NAME NAME)."
"Extra special cases for `cl-typep' predicates."
(let* ((x1 pred1) (x2 pred2)
(t1
(and (eq 'pcase--flip (car-safe x1)) (setq x1 (cdr x1))
(eq 'cl-typep (car-safe x1)) (setq x1 (cdr x1))
(and (eq 'cl-typep (car-safe x1)) (setq x1 (cdr x1))
(eq '_ (car-safe x1)) (setq x1 (cdr x1))
(null (cdr-safe x1)) (setq x1 (car x1))
(eq 'quote (car-safe x1)) (cadr x1)))
(t2
(and (eq 'pcase--flip (car-safe x2)) (setq x2 (cdr x2))
(eq 'cl-typep (car-safe x2)) (setq x2 (cdr x2))
(and (eq 'cl-typep (car-safe x2)) (setq x2 (cdr x2))
(eq '_ (car-safe x2)) (setq x2 (cdr x2))
(null (cdr-safe x2)) (setq x2 (car x2))
(eq 'quote (car-safe x2)) (cadr x2))))
(or
@ -3818,7 +3818,8 @@ STRUCT-TYPE and SLOT-NAME are symbols. INST is a structure instance."
(pcase-defmacro cl-type (type)
"Pcase pattern that matches objects of TYPE.
TYPE is a type descriptor as accepted by `cl-typep', which see."
`(pred (pcase--flip cl-typep ',type)))
`(pred (cl-typep _ ',type)))
;; Local variables:
;; generated-autoload-file: "cl-loaddefs.el"