0005391: Not commutative

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Date Submitted

Last Update

0005391

[Squeak Packages] VBRegex

minor

always

11-09-06 14:54

01-06-07 04:08

Reporter

anselm

View Status

public

Assigned To

Priority

normal

Resolution

open

Status

new

Summary

0005391: Not commutative

Description

Certain regular expressions are not commutative:

'15' matchesRegex: '[1-9]|1[0-9]'. false
'15' matchesRegex: '1[0-9]|[1-9]'. true

Seems that in the first case evaluation stops at the first expression before the '|'. Evaluation with a single character works:

'1' matchesRegex: '[1-9]|1[0-9]'. true
'1' matchesRegex: '1[0-9]|[1-9]'. true

Additional Information

Brackets don't make any difference:

'15' matchesRegex: '([1-9])|(1[0-9])'. false
'15' matchesRegex: '(1[0-9])|([1-9])'. true

'1' matchesRegex: '([1-9])|(1[0-9])'. true
'1' matchesRegex: '(1[0-9])|([1-9])'. true

Attached Files

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Notes
(0008842 - 461 - 647 - 647 - 647 - 647 - 647) nicolas cellier 01-06-07 04:08	Yes, this is a bug in regex... RxMatcher>>matchesStream: theStream "Match thyself against a positionable stream." ^(self matchesStreamPrefix: theStream) and: [stream atEnd] 15 prefix matches [1-9], so the alternative 1[0-9] is not even checked for... But the stream is not at end. So this code is wrong! Workaround: you can temporarily use an end of line matcher - $ - to obtain a correct behaviour: '15' matchesRegex: '[1-9]$\|1[0-9]'. true

Issue History
Date Modified	Username	Field	Change
11-09-06 14:54	anselm	New Issue
01-06-07 04:08	nicolas cellier	Note Added: 0008842

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