On 2019-06-30 19:52, Kaz Kylheku wrote:
On 2019-06-30 16:58, vapnik spaknik wrote:
Hi,
the regexp syntax for txr doesn't seem to include the postfix repetition operator {M,N} for matching between M & N repetitions of an object.
This is severely limiting; I need to match between 5 & 10 spaces in files I am trying to extract data from.
How can I achieve this with txr? Is it possible?
Hi vapnik,
The R{M,N} syntax basically denotes multiple expansions of R from M to N. For instance X{2,4} is a shorthand for (XX|XXX|XXXX). A match for five to ten spaces can be coded similarly.
Addendum: of course, this can be algebraically factored. For instance, in the above, we can factor out the common term XX to obtain XX(|X|XX). (Note the one empty term in the parentheses, making three).
So to match 5 to 10 spaces, first match 5 spaces, then from 0 to 5 additional: SSSSS(|S|SS|SSS|SSSS|SSSSS). For S, substitute whatever space is appropriate: the plain ASCII space or \s or whatever.
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