Rules

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

To clear the things up, here comes EBNF definition of legal expressions:

roll ::= [positive integer], "d", positive integer
entity ::= roll | positive number
expression ::= entity { [, whitespace], "+"|"*"[, whitespace], entity }

Example inputs:

  • "3d6 + 12"
  • "4*d12 + 3"
  • "d100"

Using eval functions, or similar, is not forbidden, but I encourage to solving without using these. Re-entrancy is welcome.

I cannot provide test-cases, as output should be random ;).

Format your answers' titles: language, n characters (important notes — no eval, etc.)

My ruby solution, 92 81 characters, using eval:

def f s
eval s.gsub(/(\d+)?d(\d+)/i){eval"a+=rand $2.to_i;"*a=($1||1).to_i}
end

Another ruby solution, not shorter (92 characters), but I find it interesting — it still uses eval but this time in quite creative way.

class Fixnum
def**b
eval"a+=rand b;"*a=self
end
end
def f s
eval s.gsub(/d/,'**')
end
language-agnostic dice expression-evaluation
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