Dice rolling

roll.rb

#!/usr/bin/ruby

def roll(num = 1, sides = 6, bonus = 0)
    # Rand returns a number between 1 and the argument.
    return (rand(sides-1) + 1 + bonus) * num;
end

# Parse a string in the following forms:
# - 1d4+1 or 1d4-1
# - d4+1 or d4-1
# - +1 or -1
# - 1d4
# - d4
def parse_command(command = "")
    # Split up the command.
    prefix_parts = command.split(/d/)
    suffix_parts = prefix_parts[1].split(/\+|-/)

    # The number of dice.
    num = prefix_parts[0].empty? ? 1 : prefix_parts[0].to_i

    # The type of dice.
    sides = suffix_parts[0].to_i

    # Bonus.
    bonus = suffix_parts[1].empty? ? 0 : suffix_parts[1].to_i

    # Tell the user what we're doing so if they mistyped it, they're not
    # confused.
    $stdout.write(sprintf("Rolling %d x %d-sided dice with bonus %d.", num, sides, bonus))

    return roll(num, sides, bonus)
end