dice.rb

gen=Random.new()

puts "Usage: <times>d<size>(+<mod>), add \"drop low\" or \"drop hi\" followed by amount of dice to drop to do so. 'q' to quit."
while (input=gets().chomp)!='q'
    if (cmd=/(?<roll>(?<times>\d+)[dD](?<die>\d+))\s*(?<add>(?:\s*[\+|\-]\s*\d+)*)?\s*(?:(?<drop>drop)\s*(?<dropmod>l|h)\w*\s*(?<dropN>\d)\s*\z|\z)/.match(input))!=nil
        dice=Array.new()
        cmd['times'].to_i.times do
            cmd['die'].to_i!=0 ? dice.push(gen.rand(cmd['die'].to_i)+1) : dice.push(0)
        end
        dice=dice.sort

        output=cmd['roll'] + ": "
        sum=0

        for i in 0..dice.size-1
            if i!=dice.size-1
                output = output + dice[i].to_s + ", "
            else
                output = output + dice[i].to_s
            end
                sum=sum+dice[i]
        end

        if cmd['drop']!=nil
            output=output + "; "
            if cmd['dropN'].to_i>=dice.size
                output=output + "dropped all dice, result 0."
            else
                output=output + "dropping " + (cmd['dropN']=='1' ? "the" : cmd['dropN']) + (cmd['dropmod']=='l' ? " lowest" : " highest") + (cmd['dropN']==1 ? " die; " : " dice; ")
                cmd['dropmod']=='l' ? dice=dice.drop(cmd['dropN'].to_i) : dice.pop(cmd['dropN'].to_i)
                sum=0
                for i in 0..dice.size-1
                    if i!=dice.size-1
                        output = output + dice[i].to_s + ", "
                    else
                        output = output + dice[i].to_s
                    end
                    sum=sum+dice[i]
                end
            end
        end
        output=output + "; total " + sum.to_s

        addition=cmd['add'].gsub(/\s+/, "")
        if addition!=""
            add=addition.scan(/\+|\-|\d+/)
            output=output + addition + "="

            i=0
            while i<add.size-1
                if add[i]=='+'
                    sum=sum+add[i+1].to_i
                else
                    sum=sum-add[i+1].to_i
                end
                i=i+2
            end
            output=output+sum.to_s
        end

        puts output
    else
        puts "Invalid format! Please use the format <times>d<size>(+<mod>)(\"drop lo/hi\")"
    end
end