Calculator

require 'gtk2'


class RubyApp < Gtk::Window

    def initialize
        super

        set_title "Calculator"
        signal_connect "destroy" do
            Gtk.main_quit
        end

        init_ui

        set_default_size 300, 250
        set_window_position Gtk::Window::POS_CENTER

        show_all
    end

    def init_ui
        @calc_buffer = ""
        vbox = Gtk::VBox.new false, 2

        mb = Gtk::MenuBar.new
        filemenu = Gtk::Menu.new
        file = Gtk::MenuItem.new "File"
        file.set_submenu filemenu
        mb.append file

        vbox.pack_start mb, false, false, 0

        table = Gtk::Table.new 5, 4, true

    buttons = {
            :cls   => Gtk::Button.new("Cls"),
            :bck   => Gtk::Button.new("Bck"),
            :close => Gtk::Button.new("Close"),
            :"7"   => Gtk::Button.new("7"),
            :"8"   => Gtk::Button.new("8"),
            :"9"   => Gtk::Button.new("9"),
            :/     => Gtk::Button.new("/"),
            :"4"   => Gtk::Button.new("4"),
            :"5"   => Gtk::Button.new("5"),
            :"6"   => Gtk::Button.new("6"),
            :"3"   => Gtk::Button.new("3"),
            :"2"   => Gtk::Button.new("2"),
            :"1"   => Gtk::Button.new("1"),
            :"0"   => Gtk::Button.new("0"),
            :*     => Gtk::Button.new("*"),
            :-     => Gtk::Button.new("-"),
            :+     => Gtk::Button.new("+"),
            :"="   => Gtk::Button.new("="),
            :"."   => Gtk::Button.new(".")
    }
    display = Gtk::Entry.new
    display.set_editable false
    buttons.keys.each do |key|
        if key == :"0"
            buttons[key].signal_connect("clicked") {@calc_buffer += "0"; display.text = @calc_buffer }
        elsif key.to_s.to_i != 0
            buttons[key].signal_connect("clicked") {@calc_buffer += key.to_s; display.text = @calc_buffer }
        elsif key == :close
            buttons[key].signal_connect("clicked") { Gtk.main_quit }
        elsif key == :bck
            buttons[key].signal_connect("clicked") { @calc_buffer = @calc_buffer.split(//)[0..-2].join(''); display.text = @calc_buffer}
        elsif key == :cls
            buttons[key].signal_connect("clicked") { @calc_buffer = ""; display.text = @calc_buffer }
        elsif key == :"="
            buttons[key].signal_connect("clicked") { eval("puts #{@calc_buffer}"); @calc_buffer = eval(@calc_buffer).to_s; display.text = @calc_buffer}
        else
            buttons[key].signal_connect("clicked") { @calc_buffer += key.to_s; display.text = @calc_buffer }
        end
    end

        table.attach buttons[:cls], 0, 1, 0, 1
        table.attach buttons[:bck], 1, 2, 0, 1
        table.attach Gtk::Label.new, 2, 3, 0, 1
        table.attach buttons[:close], 3, 4, 0, 1

        table.attach buttons[:"7"], 0, 1, 1, 2
        table.attach buttons[:"8"], 1, 2, 1, 2
        table.attach buttons[:"9"], 2, 3, 1, 2
        table.attach buttons[:"/"], 3, 4, 1, 2

        table.attach buttons[:"4"], 0, 1, 2, 3
        table.attach buttons[:"5"], 1, 2, 2, 3
        table.attach buttons[:"6"], 2, 3, 2, 3
        table.attach buttons[:"*"], 3, 4, 2, 3

        table.attach buttons[:"1"], 0, 1, 3, 4
        table.attach buttons[:"2"], 1, 2, 3, 4
        table.attach buttons[:"3"], 2, 3, 3, 4
        table.attach buttons[:"-"], 3, 4, 3, 4

        table.attach buttons[:"0"], 0, 1, 4, 5
        table.attach buttons[:"."], 1, 2, 4, 5
        table.attach buttons[:"="], 2, 3, 4, 5
        table.attach buttons[:"+"], 3, 4, 4, 5
        vbox.pack_start display, false, false, 0

        vbox.pack_end table, true, true, 0

        add vbox

    end
end

Gtk.init
    window = RubyApp.new
Gtk.main