simple forward-slash argument analyser and simple calc program using it with demo output

args.a-demo.txt

> calc //debug /o 1 1 /a sum
O ----
1
1

A ----
sum

2

args.rb

module Args
  def self.analyse args
    error, r = nil, {}
    flag, flags = nil, [];

    args.each_with_index do |arg, index|

      if index == 0
        if ! (arg =~ /^\/.$|^\/\/../)
          break error = true;
        end
      end

      if arg =~ /^\/.$|^\/\/../
        if index != 0 && r[flag].empty?
            r[flag] = nil;
        end
        flag = arg.sub(/\/{1,2}/, '');
        flags.push flag;
        r.store flag, [];
      else
        r[flag].push arg;
      end
    end

    if ! error && flag != nil
      if r[flag].empty?
        r[flag] = nil;
      end

      r.store "flags", flags;
      r;
    else
      nil
    end
  end
end

args = Args.analyse(ARGV);
if ! args.nil?
  case args['flags'][0]
    when "debug"
      args.delete "flags";
      args.delete "debug";
      args.each do |flag, values|
        puts "#{flag.upcase} ----", values, "\n";
      end
    when"inspect"
      puts args.inspect;
  end
end

calc.rb

require "args";

def action op, nums
  ans = 0;

  case op
    when "sum"
      nums.each do |num|
        ans += num.to_i;
      end
    when "mul"
      ans = nums.shift.to_i;
      nums.each do |num|
        ans *= num.to_i;
      end
  end
  ans;
end

def check a, o
  if ! a.nil? && ! o.nil?
    if a.length == 1 && o.length > 0
      0;
    end
  else
    nil
  end
end

def commLineError
  puts "command line error";
  exit false;
end

def syntaxError
  puts "syntax error";
  exit false;
end

## PROGRAM #####################################################################

args = Args.analyse(ARGV);

commLineError unless args
  syntaxError unless check(args['a'], args['o'])

print \
  action(
    args['a'][0],
    args['o']
  ), "\n";