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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
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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
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