Ruby find a whole math expression in a string using RegEx -


this question has answer here:

i'm trying write program take in string , use regex search mathematical expressions, such 1 * 3 + 4 / 2. operators [- * + /].

so far:

string = "something nothing 1/ 2 * 3 nothing hello world"  = /\d+\s*[\+ \* \/ -]\s*\d+/  puts a.match(string)

produces:

1/ 2

i want grab whole equation 1/ 2 * 3. i'm brand new world of regex, appreciated!

new information:

a = /\s*-?\d+(?:\s*[-\+\*\/]\s*\d+)+/

thank zx81 answer. had modify in order work. reason ^ , $ not produce output, or perhaps nil output, a.match(string). also, operators need \ before them.

version work parenthesis:

a = /\(* \s* \d+ \s* (( [-\+\*\/] \s* \d+ \)* \s* ) | ( [-\+\*\/] \s* \(* \s* \d+ \s* ))+/

regex calculators

first off, might want have @ question regex calculators (both rpn , non-rpn version).

but we're not dealing parentheses, can go like:

^\s*-?\d+(?:\s*[-+*/]\s*\d+)+$

see demo.

explanation

  • the ^ anchor asserts @ beginning of string
  • \s* allows optional spaces
  • -? allows optional minus before first digit
  • \d+ matches first digits
  • the non-capturing group (?:\s*[-+*/]\s*\d+) matches optional spaces, operator, optional spaces , digits
  • the + quantifier matches 1 or more times
  • the $ anchor asserts @ end of string

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