Tcl Source Code

I'd be happier with [string first] if
it were a true substring finder, but
it fails that task finding empty
strings:

% string first {} xyz
-1

Here's a patch to make
[string first] behave as I prefer.

This was attempted as part of TIP 323,
but was found to be too disruptive
to expectations of existing code.

If a substring finder is needed, a
new command will have to be employed
for that purpose.

File Added - 293917: 1243354-update.patch


New patch makes the [string first]
and [string last] change for
testing.

File Added: 1243354-update.patch

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Related regexp bug:

kbk% regexp -all -indices -inline -- {} foo
{0 -1} {1 0} {2 1}
kbkbut not {3 2}
kbkFWIW: % regexp -all -indices -inline -- {$} foo
{3 2}
kbkso it *can* match an empty substring at the end... but *doesn't* for an empty needle.

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Assigning to person made nervous by the thought of fixing it...

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Note that strstr() finds the empty needle at the start of
the haystack.

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Also, FWIW, this "feature"
of [string first] and [string last]
not being able to find empty
substrings may be related
to the "feature" of [string replace]
that it cannot replace empty
substrings.

File Deleted - 142950:

File Added - 142951: 1243354.patch

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FWIW, this updated patch
fixes the same issue
in [string last].

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IMO, this patch also requires patching the manual page. 

"Search string2 for a sequence of characters that exactly
match the characters in string1. If found, return the index
of the first character in the first such match within string2. "

should be changed, maybe to

"Search string2 for a substring that exactly matches
string1. If found, return the starting index of the first
such match within string2. "

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This proposed change makes me nervous ... this behavior has
been in Tcl forever:

tellar [~] 115 > tclsh7.6
% string first {} abc
-1

and I'd leave it that way, but clarify in the docs.

File Added - 142950: stringfirst.patch