re.match does not seem to support seqs

[disruptek]

This runnable example from the documentation works fine:

var matches: array[2, string]
if match("abcdefg", re"c(d)ef(g)", matches, 2):
  for s in matches:
    echo s       # => d g

Although the signature suggests that it accepts an openArray for the matches variable, match() does not populate that var if a seq is supplied instead of an array. The proc does correctly identify whether a match exists between the source string an the regular expression pattern.

Example

var matches: seq[string]
if match("abcdefg", re"c(d)ef(g)", matches, 2):
  for s in matches:
    echo s       # =>

Current Output

Expected Output

d
g

Possible Solution

Call a spade a spade and demand an array for output.

Additional Information

Nim Compiler Version 0.20.99 [Linux: amd64]
Compiled at 2019-07-15
Copyright (c) 2006-2019 by Andreas Rumpf

git hash: 8550a8127c6c80754d8a6f4300e4c77ee126e6ec
active boot switches: -d:release

[kaushalmodi]

That's an interesting bug.. I thought this would reproduce the issue, but it doesn't!: https://play.nim-lang.org/#ix=1OHl works well.

See if you can tweak that example to reproduce the bug.

Refs:

• https://nim-lang.github.io/Nim/re#match%2Ccstring%2CRegex%2CopenArray%5Bstring%5D%2Cint%2Cint
• https://github.com/nim-lang/Nim/blob/devel/lib/impure/re.nim#L265

[kaushalmodi]

Ok, the seq needs to be initialized to the required length, which can be done at run time too.

So this works: https://play.nim-lang.org/#ix=1OHt

[kaushalmodi]

May be an error should be thrown if Nim passes an unallocated or zero-length matches to pcre.

[narimiran]

Duplicate of #9472 ?

[kaushalmodi]

@narimiran Yes, this one is a duplicate.