CODEWITHSUNDEEP
regexchemistry
gaplus
gaplus

Reputation: 289

replacing text in a chemical formula string

I'm having trouble writing a function that will take a chemical formula string such as "NiNFe(AsO2)2" and remove one of the elements.
my current attempt is: 

pattern = new RegExp(symbol, "g")
formula.replace(pattern, "")

If the symbol is "N" and the formula is "NiNFe(AsO2)2" I end up with "iFe(AsO2)2" instead of the desired "NiFe(AsO2)2". Does anyone know how to code this in such a way that it would distinguish the N from the Ni and replace just that?

Upvotes: 1

Views: 196

Answers (3)

CAustin
CAustin

Reputation: 4614

If for some reason you want to avoid using negative lookahead (eg. javascript supports it but some other regex engines don't), you could simply match symbol + "([^a-z])" and replace with $1.

Upvotes: 0

Niet the Dark Absol
Niet the Dark Absol

Reputation: 324750

Use a negative lookahead. The following will also remove any quantifier it may have:

pattern = new RegExp(symbol + "(?![a-z])" + "\d*", "g");

Upvotes: 1

kennebec
kennebec

Reputation: 104810

RegExp(symbol+'(?![a-z])','g'); will match the symbol if it is not followed by a lower case letter

Upvotes: 2

Related Questions