22 — Terminal menu — a small TUI

A menu shows what can be done, lets you choose one, does it, and comes back to the menu. Because it clears the screen and draws it again, one window seems to stay alive. The clearing, the box and the rule from 14 — Screen all appear here. No quotes, no brackets, no equals sign.

#Steps

1. Draw just the menu screen first:

   clear the screen
   say in a box A small menu
   show greet
   show dice
   show quit
   draw a line
   

   copyrun it →

   The screen goes clean, the title sits in a box, the three things you can do appear, and a rule closes them off.

2. Let them choose, and branch:

   ask choice What now?
   if choice equals greet
       show Hello there!
   else if choice equals quit
       show Goodbye
   else
       show There is no such thing
   end
   

   copyrun it →

   Words are easier answers than numbers. What someone types is always text, so an answer of 1 is the letter 1 and never equals the number 1.

3. To come back to the menu, wrap the whole thing in repeat forever. The only way out is stop, so it belongs in the quit branch alone:

   repeat forever
       clear the screen
       say in a box A small menu
       show quit
       draw a line
       ask choice What now?
       if choice equals quit
           show Goodbye
           stop
       end
   end
   

   copyrun it →

4. Pause so the answer can be read. Without it the screen is wiped before anyone sees what just appeared:

   show Hello there!
   wait 1 second
   

   copyrun it →

5. The whole thing is examples/terminal-menu.nme, and the Korean twin is examples/terminal-menu.ko.nme.

   repeat forever
       clear the screen
       say in a box A small menu
       show greet
       show dice
       show quit
       draw a line
       ask choice What now?
       if choice equals greet
           show Hello there!
           wait 1 second
       else if choice equals dice
           set roll to random number from 1 to 6
           show roll
           wait 1 second
       else if choice equals quit
           show Goodbye
           stop
       else
           show There is no such thing
           wait 1 second
       end
   end
   

   copyrun it →

#Try it yourself

Add one more thing it can do. An answer of time could show how many seconds the program has been running, using the stopwatch from 15 — Time.

#What you learned

• A menu is repeat forever plus a chain of conditions. Nothing more.
• Clearing the screen at the top of the loop makes one window seem to live on.
• Words are better answers than numbers: what is typed is always text.
• wait 1 second before the screen is wiped is what makes it readable.
• stop is the only way out.