Replacing chemform in wiki - regexp

Question

could you please give me some advice, I'm replacing the <chemform> code from my wiki which is not used any more... The strings are usually simple like these:

<chemform>CH3COO-</chemform>
<chemform>Ba2+</chemform>
<chemform>H2CO3</chemform>

I need them to be replaced by these:

CH<sub>3</sub>COO<sup>-</sup>
Ba<sub>2</sub><sup>+</sup>
H<sub>2</sub>CO<sub>3</sub>

So far I came up with this regexp for the RegExr tool:

match: <chemform\b[^>]*>(\D*?)([0-9]*)(\D*?)(\D*?)([0-9]*)(\D*?)([-+]*?)</chemform>

replace: $1$2$3$4$5$6$7

I know the code is horrible, but so far it's been working for me except for the fact it's getting me empty strings like :

<sub></sub>CH<sub>3</sub>COO<sup>-</sup>
<sub></sub>Ba<sub>2</sub><sup>+</sup>
H<sub>2</sub>CO<sub>3</sub><sup></sup>

How can I get rid of these without doing second replace search? Thanks a lot!

Won't work for eg `NH4C2H3O2`. Pretty much for the same reason. You could use regex to match `` tags, then use a separate function to parse and create the replacement. — Qtax, Jun 19 '12 at 22:24
Do you have the input that resulted in the empty strings shown above? — David, Jun 19 '12 at 22:27

PJProudhon · Answer 1 · 2017-10-15T08:40:21.110

You could use Notepad++, which is able to proceed to conditional replacements (you can have details in that previous post from Wiktor Stribiżew).

Use the following patterns:

match: ([A-Za-z]+(?=[-+\d]))(?\d+)?(?[-+])?(?=[-+\w]*</chemform>)
replace: $1(?{sub}$+{sub})(?{sup}$+{sup})

Given your input sample, I get:

<chemform>CH<sub>3</sub>COO<sup>-</sup></chemform>  
<chemform>Ba<sub>2</sub><sup>+</sup></chemform>  
<chemform>H<sub>2</sub>CO<sub>3</sub></chemform>

Replacing chemform in wiki - regexp

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