Regular Expressions: replacing empty patterns only works correctly in nre

[skilchen]

Using nre:

import nre
echo replace("bar", re"^", "foo")
echo replace("foo", re"$", "bar")
echo replace("foo", re"", "-")

produces:

foobar
foobar
-f-o-o-

as expected.

Using re instead:

import re
echo replace("bar", re"^", "foo")
echo replace("foo", re"$", "bar")
echo replace("foo", re"", "-")

each replace ends in an infinite loop.

And @nitely's Module regex

import regex
echo replace("bar", re"^", "foo")
echo replace("foo", re"$", "bar")
echo replace("foo", re"", "-")

produces:

foobfooafoor
fobarbarbarfoo
-f-o-o

which doesn't make much sense... But this is not a Nim issue.

[Araq]

Endless loops are just as fine here IMO, garbage in, garbage out.

[kaushalmodi]

I ended up on re replace entering an endless loop just yesterday, for a simple toy example:

import re 
echo replace("hello", re"$", "!") # expected "hello!", but inflooped

[kaushalmodi]

Endless loops are just as fine here IMO, garbage in, garbage out.

I didn't follow.

[skilchen]

@Araq

Endless loops are just as fine here IMO, garbage in, garbage out.

Neither the empty string nor zero-length matches are garbage.