Tcl Source Code

In the following example, the resulting indices are wrong:

% regexp -indices -inline {(?:a*b)+c} aaaabbbbcc
{0 8}

The correct result should be:

% regexp -indices -inline {(?:a*b)+c} aaaabbbbcc
{7 8}

No.

Although the sub-expression traverses over all a (and finally over all b without a), despite this not capturing it as a group - the whole expression matches all characters to first c inclusive it.

So the result {0 8} is pretty correct - {0..4} aaaab within first iteration by a*b, {5..7} bbb within second to 4th iteration by (a*b)+ and then finally {8} c.

Note that (?:a*b)+ is neither a lookahead nor a lookbehind assertion (which is not implemented in tcl at all), so the whole match is captured for whole expression.

How the iterations for first subexpression look, illustrating this example:

    % regexp -all -indices -inline {a*b} aaaabbbbcc
    {0 4} {5 5} {6 6} {7 7}