diff options
| -rw-r--r-- | share/txr/stdlib/awk.tl | 18 | ||||
| -rw-r--r-- | txr.1 | 30 |
2 files changed, 43 insertions, 5 deletions
diff --git a/share/txr/stdlib/awk.tl b/share/txr/stdlib/awk.tl index 7c6ae504..07a5f3bc 100644 --- a/share/txr/stdlib/awk.tl +++ b/share/txr/stdlib/awk.tl @@ -48,6 +48,7 @@ begin-actions end-actions cond-actions (nranges 0) + (rng-rec-temp (gensym)) rng-expr-temps rng-exprs) @@ -109,6 +110,11 @@ (t (put-string self.rec) (put-string self.ors)))) +(defun sys:range-test (val rec) + (caseq (typeof val) + ((regex fun) (call val rec)) + (t val))) + (defun sys:awk-expander (clauses) (let ((awc (new sys:awk-compile-time))) (each ((cl clauses)) @@ -176,7 +182,7 @@ (macrolet ((next () '(return-from :awk-rec)) (next-file () '(return-from :awk-file)) (prn (. args) ^(qref ,',aws-sym (prn ,*args))) - (rng (from-expr to-expr :env e) + (sys:rng (from-expr to-expr :env e) (let ((ix (pinc (qref ,awc nranges))) (rng-temp (gensym)) (from-expr-ex (sys:expand from-expr e)) @@ -193,6 +199,9 @@ (or (set flag ,flag-new) ,flag-old))) (qref ,awc rng-exprs)) rng-temp)) + (rng (from-expr to-expr) + ^(sys:rng (sys:range-test ,from-expr ,(qref ,awc rng-rec-temp)) + (sys:range-test ,to-expr ,(qref ,awc rng-rec-temp)))) (ff (. opip-args) ^(symacrolet ((f (rslot ,',aws-sym 'fields 'f-to-rec))) (set f [(opip ,*opip-args) f]))) @@ -229,9 +238,10 @@ ,*awc.end-file-actions)))) (,awk-fun (lambda (,aws-sym) ,(if awc.rng-exprs - ^(let* ,(nreverse - (zip awc.rng-expr-temps - awc.rng-exprs)) + ^(let* ((,awc.rng-rec-temp rec) + ,*(nreverse + (zip awc.rng-expr-temps + awc.rng-exprs))) ,p-actions-xform) p-actions-xform)))) ,*awc.begin-actions @@ -38771,7 +38771,25 @@ The expressions .meta from-condition and .meta to-condition -are ordinary expressions which are evaluated; however, the are evaluated +are ordinary expressions which are evaluated. However, their +evaluation is unusual in two ways. + +Firstly, if either expression +produces, as its result, a function or regular expression object, +then that function or regular expression object is applied to +the current record (value of the +.code rec +variable), and the result of that application is then taken +as the result of the condition. This allows for expressions like +.code "(rng (f^ #/start/) #/end/)" +which denotes a range which begins with a record which +begins with the prefix +.str start +and ends with a record which contains +.str end +as a substring. + +Secondly, the conditions are evaluated out of order with respect to the surrounding expression in which they occur. Ranges and their constituent .meta from-condition @@ -38813,6 +38831,16 @@ itself is evaluated, the expression merely fetches a previously computed Boolean value which indicates whether the range is active for this record. +Also, the behavior is unspecified if range expressions attempt to modify +the awk-special variables. +.codn rec , +.codn f , +.codn fs , +.code ft +or +.codn kfs . +It is not recommended to place any side effects into range expressions. + Evaluation of ranges obeys the following logic, which is applied to each range, prior to the processing of condition-action clauses. If a range is not currently active, its |