retroforth/example/99-bottles.retro

# 99 Bottles

Display the text for the *99 Bottles of Beer* song.

For this, I'm using `s:evaluate` to construct words which
display a string when called. This lets the majority of the
code read nicely.

~~~
{ 'bottle 'bottles 'of 'beer 'on 'the 'wall 'no 'more
  'Take 'one 'down, 'pass 'it 'around }
[ dup ':%s_'%s_s:put_sp_; s:format s:evaluate ] a:for-each
~~~

Handling of the exact text related to the number of bottles
is done with a simple array of functions that get selected
based on the number of bottles left. This is done with a
very simple filter, where the number of bottles for the
purpose of the text is in a set of 2 or more, 1, or none.

~~~
{ [ no more bottles      ]
  [ #1 n:put sp bottle   ]
  [ dup n:put sp bottles ]
} 'BOTTLES const

:number-bottles
  dup #2 n:min BOTTLES swap a:fetch call ;
~~~

Thanks to the programatically generated words for the
verse text, the main code is nicely readable.

~~~
:display-verse
  number-bottles of beer on the wall  nl
  number-bottles of beer              nl
  n:dec Take one down, pass it around nl
  number-bottles of beer on the wall  nl ;

:verses (n-)
  repeat 0; nl display-verse again ;

#99 verses 
~~~