ruby regexp to replace equations

Question

I have a some HTML text in mathjax format:

text = \"an inline \\\\( f(x) = \\frac{a}{b} \\\\) equation, a display equation \\\\[ F = m a \\\\] \\n and anothe         


        

Answer 1

Try:

desired = text.gsub(/\\\[\s*(.*?)\s*\\\]/, "<img src=\"http://latex.codecogs.com/png.latex?\\1\"/>") 
desired = desired.gsub(/\\\(\s*(.*?)\s*\\\)/, "<img src=\"http://latex.codecogs.com/png.latex?\\1\inline\"/>")
desired

The important changes that had to happen:

• The first parameter for gsub should be a regex (as Anthony mentioned)
• If the second parameter is a double-quoted string, then the back references have to be like \\2 (instead of just \2) (see the rdoc)
• The first parameter was not escaping the \

There were a couple of other minor formatting things (spaces, etc).

Answer 2

Not sure if your regexp is right - but in Ruby, Regexp are delimited by //, try like this :

desired = text.gsub(/(\\[)(.*?)(\\])/, "<img src=\"http://latex.codecogs.com/png.latex?\2\" />")

You were trying to do string substition, and of course gsub wasn't finding a string containing (\\[)(.*?)(\\])