diff options
| -rw-r--r-- | share/txr/stdlib/match.tl | 12 | ||||
| -rw-r--r-- | txr.1 | 47 |
2 files changed, 33 insertions, 26 deletions
diff --git a/share/txr/stdlib/match.tl b/share/txr/stdlib/match.tl index ea0134fc..f99a8fe6 100644 --- a/share/txr/stdlib/match.tl +++ b/share/txr/stdlib/match.tl @@ -446,15 +446,11 @@ obj-var obj-var guard-chain (list dj-guard))))) -(defun compile-and-match (par-pat obj-var var-list) - (mac-param-bind *match-form* (op . pats) par-pat - (let* ((var-lists (mapcar (ret (copy var-list)) pats)) - (par-matches (mapcar (op compile-match @1 obj-var @2) - pats var-lists))) - (each ((vl var-lists)) - var-list.(merge vl)) +(defun compile-and-match (and-pat obj-var var-list) + (mac-param-bind *match-form* (op . pats) and-pat + (let* ((par-matches (mapcar (lop compile-match obj-var var-list) pats))) (new compiled-match - pattern par-pat + pattern and-pat obj-var obj-var guard-chain (mappend .guard-chain par-matches))))) @@ -40307,15 +40307,11 @@ operator succeeds if .meta pattern matches. -Note: the -.code and -operator can be used to bind a variable to an object, with back-referencing, in -parallel with other patterns which also match the object. However, all of the -elements of -.code and -are in separate scopes; back-referencing among branches of an +Note: in a situation when it is necessary to bind a variable to an object +in parallel with one or more patterns, such that the variable can back-reference +to an existing occurrence, the .code and -isn't possible. +pattern operator can be used. .TP* Example: @@ -40598,24 +40594,39 @@ operator requires one to match. It tries the patterns in left to right order, and stops at the first matching one, declaring failure if none match. +The +.code and +and +.code or +operators have different scoping rules. +Under +.codn and , +later patterns are processed in the scopes of earlier patterns, +just like with other pattern operators. Duplicate variables +back-reference. +Under +.codn or , +the patterns are processed in separate, parallel scopes. +No back-referencing takes place among same-named variables +introduced in separate patterns of the same +.codn or . + When the .code and matches, the variables from all of the -patterns are bound. Duplicate variables from multiple patterns are merged into -a single instance. The rightmost occurrence of a variable takes precedence; its -value is the one that appears. - +patterns are bound. When the .code or operator matches, the variables from all of the patterns -are bound. -The variables from the matching +are also bound. However, only the variables from the matching .meta pattern take on the values implied by that pattern. -The variables from the non-matching patterns that are not -duplicates of variables in the matching -.meta pattern -take on +The variables from the non-matching patterns that do not have +the same names as variables in the matching +.metn pattern , +and that have been newly introduced in the +.code or +operator, take on .code nil values. |