ByteString>>match: greedyness of * ??

Hello,

I found the following results for some expressions using #match:

'e' match: 'e'.   "true"
'*' match: 'e'.   "true"
'#' match: 'e'.   "true"

'*e' match: 'e'.  "true"
'*#' match: 'e'.  "false"
'**' match: 'e'.  "false"

'*' match: ''.    "true"
'**' match: ''.   "false"


Is this expected behavior?
Looks like * is sometimes 'greedy', sometimes not. (Comparing 4 and 5)
Thank you for any hints.

Christoph
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This behavior is squeakish, other Smalltalk match differently:

VW:  '**' match: 'e'. "true"
gst: '**' match: 'e'. "true"

Anyway, this pattern matching is limited. How do you match a '*' itself?
I thought your example might be interpreted as an escape sequence, but
no, there is no escape in this simple matching.

'**' match: '*'. "false"
'\*' match: '*'. "false"

Try VBregex or another regex package.

Nicolas


Ch Lamprecht a écrit :
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nicolas cellier wrote:
Hi,
thank you.
In addition to the expressions below, I found, that #match: does not behave as
stated by the comment given in the method definition itself:

 From ByteString>>match:

"
        [snip]
        'foo*baz' match: 'foo23baz' true
        'foo*baz' match: 'foobaz' true    <----
        'foo*baz' match: 'foo23bazo' false
        'foo' match: 'Foo' true
        'foo*baz*zort' match: 'foobazort' false
        'foo*baz*zort' match: 'foobazzort' false <----
        [snip]
"

confused, Christoph

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On Tuesday 08 January 2008 13:03:22 Ch Lamprecht wrote:
In general * means any character including no characters.

So the first one is foo any-character baz.

The third is false because of the "o" on the end.  If you wanted it to work
you could put 'foo*baz*'.

I don't know why the last one wasn't reported as true.


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Hello,

I browsed String>>startingAt:match:startingAt:

and changed two lines to make errorhandling work as probably intended by the
author.

startingAt: keyStart match: text startingAt: textStart
        "Answer whether text matches the pattern in this string.
        Matching ignores upper/lower case differences.
        Where this string contains #, text may contain any character.
        Where this string contains *, text may contain any sequence of characters."
        | anyMatch matchStart matchEnd i matchStr j ii jj |
        i := keyStart.
        j := textStart.

        "Check for any #'s"
        [i > self size ifTrue: [^ j > text size "Empty key matches only empty string"].
        (self at: i) = $#] whileTrue:
                ["# consumes one char of key and one char of text"
                j > text size ifTrue: [^ false "no more text"].
                i := i+1.  j := j+1].

        "Then check for *"
        (self at: i) = $*
                ifTrue: [i = self size ifTrue:
                                        [^ true "Terminal * matches all"].
                                "* means next match string can occur anywhere"
                                anyMatch := true.
                                matchStart := i + 1]
                ifFalse: ["Otherwise match string must occur immediately"
                                anyMatch := false.
                                matchStart := i].

        "Now determine the match string"
        matchEnd := self size.
        (ii := self indexOf: $* startingAt: matchStart) > 0 ifTrue:


"changed the following line to:"
                [ii = matchStart  ifTrue: [self error: '** not valid -- use * instead'].
                matchEnd := ii-1].
        (ii := self indexOf: $# startingAt: matchStart) > 0 ifTrue:


"changed the following line to:"
                [ii = matchStart  ifTrue: [self error: '*# not valid -- use #* instead'].
                matchEnd := matchEnd min: ii-1].
        matchStr := self copyFrom: matchStart to: matchEnd.

        "Now look for the match string"
        [jj := text findString: matchStr startingAt: j caseSensitive: false.
        anyMatch ifTrue: [jj > 0] ifFalse: [jj = j]]
                whileTrue:
                ["Found matchStr at jj.  See if the rest matches..."
                (self startingAt: matchEnd+1 match: text startingAt: jj + matchStr size) ifTrue:
                        [^ true "the rest matches -- success"].
                "The rest did not match."
                anyMatch ifFalse: [^ false].
                "Preceded by * -- try for a later match"
                j := j+1].
        ^ false "Failed to find the match string"



Kent Loobey wrote: _______________________________________________
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