Evaluate dice rolling notation strings

Question

Rules

Write a function that accepts string as a parameter, returning evaluated value of expression in dice notation, including addition and multiplication.

To

Answer 1

Ruby, 166 characters, no eval

In my opinion quite elegant ;).

def g s,o=%w{\+ \* d}
o[a=0]?s[/#{p=o.pop}/]?g(s.sub(/(\d+)?\s*(#{p})\s*(\d+)/i){c=$3.to_i
o[1]?($1||1).to_i.times{a+=rand c}+a:$1.to_i.send($2,c)},o<

Deobfuscated version + comments:

def evaluate(string, opers = ["\\+","\\*","d"])
  if opers.empty?
    string
  else
    if string.scan(opers.last[/.$/]).empty? # check if string contains last element of opers array

      # Proceed to next operator from opers array.

      opers.pop
      evaluate(string, opers)

    else # string contains that character...

      # This is hard to deobfuscate. It substitutes subexpression with highest priority with
      # its value (e.g. chooses random value for XdY, or counts value of N+M or N*M), and
      # calls recursively evaluate with substituted string.

      evaluate(string.sub(/(\d+)?\s*(#{opers.last})\s*(\d+)/i) { a,c=0,$3.to_i; ($2 == 'd') ? ($1||1).to_i.times{a+=rand c}+a : $1.to_i.send($2,c) }, opers)

    end
  end
end