# From arnold  Thu May  9 17:27:03 2002
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# From: Aharon Robbins <arnold@skeeve.com>
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# Subject: fixme
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# From: laura@madonnaweb.com (laura fairhead)
# Newsgroups: comp.lang.awk
# Subject: bug in gawk3.1.0 regex code
# Date: Wed, 08 May 2002 23:31:40 GMT
# Organization: that'll be the daewooo :)
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# 
# 
# I believe I've just found a bug in gawk3.1.0 implementation of
# extended regular expressions. It seems to be down to the alternation
# operator; when using an end anchor '$' as a subexpression in an
# alternation and the entire matched RE is a nul-string it fails
# to match the end of string, for example;
# 
# gsub(/$|2/,"x")
# print
# 
# input           = 12345
# expected output = 1x345x
# actual output   = 1x345
# 
# The start anchor '^' always works as expected;
# 
# gsub(/^|2/,"x")
# print
# 
# input           = 12345
# expected output = x1x345
# actual output   = x1x345
# 
# This was with POSIX compliance enabled althought that doesn't
# effect the result.
# 
# I checked on gawk3.0.6 and got exactly the same results however
# gawk2.15.6 gives the expected results.
# 
# I'm about to post a bug report about this into gnu.utils.bug
# but I thought I'd post it here first in case anyone has
# any input/comments/whatever ....
# 
# Complete test results were as follows;
# 
# input          12345
# output         gsub(/regex/,"x",input)
# 
# regex          output
# (^)            x12345
# ($)            12345x
# (^)|($)        x12345x
# ($)|(^)        x12345x
# (2)            1x345
# (^)|2          x1x345
# 2|(^)          x1x345
# ($)|2          1x345
# 2|($)          1x345
# (2)|(^)        x1x345
# (^)|(2)        x1x345
# (2)|($)        1x345
# ($)|(2)        1x345
# .((2)|(^))     x345
# .((^)|(2))     x345
# .((2)|($))     x34x
# .(($)|(2))     x34x
# x{0}((2)|(^))  x1x345
# x{0}((^)|(2))  x1x345
# x{0}((2)|($))  1x345
# x{0}(($)|(2))  1x345
# x*((2)|(^))    x1x345
# x*((^)|(2))    x1x345
# x*((2)|($))    1x345
# x*(($)|(2))    1x345
# 
# Here's the test program I used, a few of the cases use ERE {n[,[m]]}
# operators so that will have to be commented out or have a check
# added or something (should have put a conditional in I know... ;-)
# 
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# 
BEGIN{

TESTSTR="12345"

print "input          "TESTSTR
print "output         gsub(/regex/,\"x\",input)"
print ""

print "regex          output"
$0=TESTSTR
gsub(/(^)/,"x")
print "(^)            "$0

$0=TESTSTR
gsub(/($)/,"x")
print "($)            "$0

$0=TESTSTR
gsub(/(^)|($)/,"x")
print "(^)|($)        "$0

$0=TESTSTR
gsub(/($)|(^)/,"x")
print "($)|(^)        "$0

$0=TESTSTR
gsub(/2/,"x")
print "(2)            "$0

$0=TESTSTR
gsub(/(^)|2/,"x")
print "(^)|2          "$0

$0=TESTSTR
gsub(/2|(^)/,"x")
print "2|(^)          "$0

$0=TESTSTR
gsub(/($)|2/,"x")
print "($)|2          "$0

$0=TESTSTR
gsub(/2|($)/,"x")
print "2|($)          "$0

$0=TESTSTR
gsub(/(2)|(^)/,"x")
print "(2)|(^)        "$0

$0=TESTSTR
gsub(/(^)|(2)/,"x")
print "(^)|(2)        "$0

$0=TESTSTR
gsub(/(2)|($)/,"x")
print "(2)|($)        "$0

$0=TESTSTR
gsub(/($)|(2)/,"x")
print "($)|(2)        "$0

$0=TESTSTR
gsub(/.((2)|(^))/,"x")
print ".((2)|(^))     "$0

$0=TESTSTR
gsub(/.((^)|(2))/,"x")
print ".((^)|(2))     "$0

$0=TESTSTR
gsub(/.((2)|($))/,"x")
print ".((2)|($))     "$0

$0=TESTSTR
gsub(/.(($)|(2))/,"x")
print ".(($)|(2))     "$0

$0=TESTSTR
gsub(/x{0}((2)|(^))/,"x")
print "x{0}((2)|(^))  "$0

$0=TESTSTR
gsub(/x{0}((^)|(2))/,"x")
print "x{0}((^)|(2))  "$0

$0=TESTSTR
gsub(/x{0}((2)|($))/,"x")
print "x{0}((2)|($))  "$0

$0=TESTSTR
gsub(/x{0}(($)|(2))/,"x")
print "x{0}(($)|(2))  "$0

$0=TESTSTR
gsub(/x*((2)|(^))/,"x")
print "x*((2)|(^))    "$0

$0=TESTSTR
gsub(/x*((^)|(2))/,"x")
print "x*((^)|(2))    "$0

$0=TESTSTR
gsub(/x*((2)|($))/,"x")
print "x*((2)|($))    "$0

$0=TESTSTR
gsub(/x*(($)|(2))/,"x")
print "x*(($)|(2))    "$0

$0=TESTSTR
gsub(/x{0}^/,"x")
print "x{0}^          "$0

$0=TESTSTR
gsub(/x{0}$/,"x")
print "x{0}$          "$0

$0=TESTSTR
gsub(/(x{0}^)|2/,"x")
print "(x{0}^)|2      "$0

$0=TESTSTR
gsub(/(x{0}$)|2/,"x")
print "(x{0}$)|2      "$0


}
# 
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# 
# byefrom
# 
# -- 
# laura fairhead  # laura@madonnaweb.com  http://lf.8k.com
#                 # if you are bored crack my sig.
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