Hello,
The short-circuit words were all special cased based on arity. Now they are
defined in terms of n&&-rewrite and n||-rewrite words. Here's n&&-rewrite:
:: n&&-rewrite ( quots N -- quot )
quots
[ '[ drop N ndup @ dup not ] [ drop N ndrop f ] 2array ]
map
[ t ] [ N nnip ] 2array suffix
'[ f , cond ] ;
The variants are now just:
MACRO: 0&& ( quots -- quot ) 0 n&&-rewrite ;
MACRO: 1&& ( quots -- quot ) 1 n&&-rewrite ;
MACRO: 2&& ( quots -- quot ) 2 n&&-rewrite ;
Can 'n&&-rewrite' be improved? Here's a "holy grail" version of 'n&&-rewrite'
using some non-existent syntax features:
:: n&&-rewrite ( qs N -- quot )
'[
f
{
@[ qs [| Q | { [ drop N ndup Q@ dup not ] [ drop N ndrop f ] } ] map ]
{ [ t ] [ N nnip ] }
}
cond
] ;
The features:
* Locals inside literal arrays
* @[ ... ] means splice the result of calling the ...
* There's a local named 'Q' specified in the lambda.
Q@ means to splice the value.
At this point I'd like to send a little shout-out to Chris Double. When he
introduced the n* general arity shuffle words, their value was questioned. It
was said that if you need them, you should refactor your code. Well
eventually macros came along and the code that writes code renaissance began.
It turns out that for general macros like n&&-rewrite, the n* macros are
essential. I'm very glad we have them.
Ed
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