diff options
| -rw-r--r-- | share/txr/stdlib/match.tl | 4 | ||||
| -rw-r--r-- | txr.1 | 37 |
2 files changed, 29 insertions, 12 deletions
diff --git a/share/txr/stdlib/match.tl b/share/txr/stdlib/match.tl index 09f1c068..0c672903 100644 --- a/share/txr/stdlib/match.tl +++ b/share/txr/stdlib/match.tl @@ -180,9 +180,9 @@ var-exprs (append car-match.var-exprs cdr-match.var-exprs))))) (defun compile-require-match (exp obj-var) - (mac-param-bind *match-form* (op match condition) exp + (mac-param-bind *match-form* (op match . conditions) exp (let ((match (compile-match match obj-var))) - (set match.test-expr ^(and ,condition ,match.test-expr)) + (set match.test-expr ^(and ,match.test-expr ,*conditions)) match))) (defun compile-let-match (exp obj-var) @@ -39934,7 +39934,7 @@ as its value. .coNP Pattern operator @ require .synb -.mets @(require < pattern << expression *) +.mets @(require < pattern << condition *) .syne .desc The pattern operator @@ -39944,19 +39944,36 @@ applies the specified to the corresponding object. If the .meta pattern -matches, the operator then imposes the additional conditions specified by -the extra -.metn expression . -The -.meta expression +matches, the operator then imposes the additional constraints +specified by zero or more +.meta condition +forms. +Each +.meta condition is evaluated in a scope in which the variables from .meta pattern have already been established. -However, the mach is considered to have succeeded only if -.meta expression -yields true. If it yields + +For the +.code require +operator to be a successful match, every +.meta condition +must evaluate true, otherwise the match fails. + +The +.meta condition +forms behave as if they were the arguments of an implicit +.code and +operator, which implies left-to-right evaluation behavior, stopping +evaluation on the first +.meta condition +which produces .codn nil , -then the match is deemed to have failed. +and defaulting to a result of +.code t +when no +.meta condition +forms are specified. .TP* Examples: |