Regular expression debugger and optimizer.

UNDER DEVELOPMENT! PRs welcome.

Just clone and use stack to build

$ git clone https://github.com/gciruelos/egregex
$ cd egregex
$ stack build

egregex can show examples of strings that match a given regular expression.

$ stack exec egregex -- --show-matches=10 "a+b*c+"
ac
aac
acc
abc
aaac
aacc
aabc
accc
abcc
abbc

If no parameter is supplied to --show-matches then it will enumerate all the strings that match the given regular expression

egregex can also show examples of strings that do not match a given regular expression.

$ stack exec egregex -- --show-mismatches=12 "a+b*c+"
a
b
c

aa
ab
ba
bb
bc
ca
cb
cc

The empty line is the empty string.

egregex can also enumerate strings that match or don't match several different regular expressions.

$ stack exec egregex -- --matches="a+b*c+" --matches="a*b+c*" --doesnt-match="a*c" --show-matches=12
abc
aabc
abcc
abbc
aaabc
aabcc
aabbc
abccc
abbcc
abbbc
aaaabc
aaabcc

egregex allows the user to obtain an optimized (shorter) version of a given regular expression.

$ stack exec egregex -- -O1 "a*a+"
a+

It can also to merge several requirements into a single regular expression.

$ stack exec egregex -- --matches="a+b*c+" --matches="ab+c*" --doesnt-match="abc" -O1
ab((cc)|(b+c))c*

If the user wants a faster result in exchange for a worse resulting regular expression, they can choose a lower optimization level.

$ stack exec egregex -- --matches="a+b*c+" --matches="ab+c*" --doesnt-match="abc" -O0
ab((cc)|(bb*c)))|(ab((cc)|(bb*c))c*(c|)

$ stack exec egregex -- --matches="a*b+c*" --doesnt-match="a*b+c*" --show-matches=3

$ stack exec egregex -- --matches="a*b+c*" --doesnt-match="a*b+c*" -O0
<impossible>

• Debugging capabilities, as in understanding why a regex doesn't match a given string. For example,

$ stack exec regex -- debug="hello" "he(lll)+o"

• Cleaner and faster code.