From dd3884648c375a775ed1e777e5f8f58db5d226d7 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Fri, 19 May 2017 20:36:45 -0700
Subject: awk: new feature: again operator.

* share/txr/stdlib/awk.tl (sys:awk-state loop):
Wrap a loop around around the two forms that
split the record into fields and dispatch the main
rule function. The loop repeats if the named
block returns :awk-again.
(sys:awk-mac-let): New local macro (again)
which bails out of the :awk-rec block just like (next) does,
but specifies :awk-again as the return value.

* txr.1: Documented.
---
 share/txr/stdlib/awk.tl |  6 +++---
 txr.1                   | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/share/txr/stdlib/awk.tl b/share/txr/stdlib/awk.tl
index 5b19e706..b0f54aaf 100644
--- a/share/txr/stdlib/awk.tl
+++ b/share/txr/stdlib/awk.tl
@@ -172,9 +172,8 @@
               (set aws.rec rec aws.orig-rec rec)
               (inc aws.rec-num)
               (inc aws.file-rec-num)
-              aws.(rec-to-f)
-              (block :awk-rec
-                [func aws]))
+              (while* (eq :awk-again (block :awk-rec [func aws]))
+                aws.(rec-to-f)))
             (when end-file-func
               [end-file-func aws])))))))
 
@@ -294,6 +293,7 @@
                 (ofs (qref ,aws-sym ofs))
                 (ors (qref ,aws-sym ors)))
      (macrolet ((next () '(return-from :awk-rec))
+                (again () '(return-from :awk-rec :awk-again))
                 (next-file () '(return-from :awk-file))
                 (sys:rng (form from-expr to-expr :env e)
                   (let ((style (car form))
diff --git a/txr.1 b/txr.1
index cff7cd87..6ac4422a 100644
--- a/txr.1
+++ b/txr.1
@@ -45022,6 +45022,31 @@ record,
 .code awk
 terminates.
 
+.coNP Macro @ again
+.synb
+.mets (again)
+.syne
+.desc
+The awk macro
+.code again
+may be invoked in a condition-pattern clause. It terminates the
+processing of that clause, and all subsequent clauses.
+Then, the current value of the record, namely the datum stored
+in the Awk variable
+.codn rec ,
+is delimited into fields, and all of the condition-pattern clauses
+are processed again.
+
+No other state is modified. In particular, the record number
+.code nr
+and the
+.code orec
+variable holding the original record both retain their current values.
+
+Note: this is an original feature in the \*(TL
+.code awk
+macro, which has no counterpart in POSIX or GNU Awk.
+
 .coNP Macro @ next-file
 .synb
 .mets (next-file)
-- 
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