[TW5] regexp

[John]

Filter search using search[{{}}] shows a tiddler about transclusion.

But Filter search using regexp[{{[a-zA-Z0-9]*}}] does not yield the same result.

Why not?

[Eric Shulman]

On Saturday, August 15, 2015 at 12:32:44 AM UTC-7, John wrote:

Filter search using search[{{}}] shows a tiddler about transclusion.

But Filter search using regexp[{{[a-zA-Z0-9]*}}] does not yield the same result.

1) you need to search in the correct field

By default, search[{{}}] look in both the tiddler title and content.  There is one tiddler, [[Transclusion Basic Usage]] that contains the literal "{{}}".

However, regexp[{{}}] defaults to only the title field, and there are no tiddler *titles* that include the curly braces, thus no results.

To apply a regexp filter on the tiddler content, you need specify the desired field by writing regexp:text[...]

2) The documentation in http://tiddlywiki.com/#regexp%20Operator says this:

"The filter syntax makes it impossible to directly specify a regular expression that contains square brackets. The solution is to store the expression in a variable. See the examples."

Thus, to run the filter you want, you can't use the Advanced Search/Filter tab.  Instead, you need to write something like this into a tiddler:

<$set name="pattern" value="{{[a-zA-Z0-9]*}}">
<<list-links "[regexp:text<pattern>]">>
</$set>

Hope this helps,

enjoy,

-e

Eric Shulman

ELS Design Studios

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[John]

Thanks for the explanation.

[PMario]

also see: https://groups.google.com/forum/#!topic/tiddlywiki/fLK0op_GqGA
-m

[hexa...@gmail.com]

Thanks a lot.

But further, if I want to catch the match like this:

```

<$set name="pattern" value="{{the (.*?) thing}}">

<<list-links "[regexp:text<pattern>]">>
</$set> 

``` 
How can I get the (.*?)'s value?

[Eric Shulman]

On Saturday, October 10, 2020 at 1:06:50 AM UTC-7, hexa...@gmail.com wrote:

Thanks a lot.

But further, if I want to catch the match like this:

```

<$set name="pattern" value="{{the (.*?) thing}}">
<<list-links "[regexp:text<pattern>]">>
</$set> 

``` 
How can I get the (.*?)'s value?

The TWCore regexp[...] filter only tests for a match, but doesn't support extracting "grouped" text matches (i.e., embedded patterns surrounded by parentheses).

However, there is an add-on filter named regexps[...] (the "s" is for string) that DOES return the matching group(s)...

https://github.com/Marxsal/TiddlyWiki5/blob/regular_expression_strings/core/modules/filters/regexps.js

If you copy the above code into a tiddler (e.g., $:/filters/regexps.js) and then save-and-reload, you can then use regexps:text<pattern> to get the matched text.

enjoy,

-e