awk macro: fix buggy range semantics.

* share/txr/stdlib/awk.tl (sys:awk-let): The closing
expression of an awk range only applies when
the range is active. Refactor generated code with local flags to
eliminate duplicating the end range expression.
Avoid evaluating the start range expression if the
range is already active.

1 files changed, 9 insertions, 5 deletions

diff --git a/share/txr/stdlib/awk.tl b/share/txr/stdlib/awk.tl
index 4c40494a..f3b80a79 100644
--- a/share/txr/stdlib/awk.tl
+++ b/share/txr/stdlib/awk.tl
@@ -143,13 +143,17 @@
                   (let ((ix (pinc (qref ,awc nranges)))
                         (rng-temp (gensym))
                         (from-expr-ex (sys:expand from-expr e))
-                        (to-expr-ex (sys:expand to-expr e)))
+                        (to-expr-ex (sys:expand to-expr e))
+                        (flag-old (gensym))
+                        (flag-new (gensym)))
                     (push rng-temp (qref ,awc rng-expr-temps))
                     (push ^(placelet ((flag (vecref (qref ,',aws-sym rng-vec) ,ix)))
-                             (cond
-                               (,from-expr-ex (set flag t))
-                               (,to-expr-ex (zap flag) t)
-                               (flag)))
+                             (let* ((,flag-old flag) ,flag-new)
+                               (when (or ,flag-old ,from-expr-ex)
+                                 (set ,flag-new t))
+                               (when (and ,flag-new ,to-expr-ex)
+                                 (set ,flag-new nil))
+                               (or (set flag ,flag-new) ,flag-old)))
                           (qref ,awc rng-exprs))
                     rng-temp)))
        ,*body)))