Hi,
Eric nicely gave me his solution :
DEFER: combinations
: (combinations) [ 1 tail ] dip combinations ;
: prefix-each [ prefix ] curry map ;
: combinations ( seq n -- seqs )
{
{ [ dup 0 = ] [ 2drop { { } } ] }
{ [ over empty? ] [ 2drop { } ] }
{ [ t ] [
Hi,
Your code is faster because it short-cuts sooner when you know the
result of an operation. Because of your condition,
{ [ 2dup = ] [ 3drop 1array ] }
your code can jump to the conclusion that { 1 2 3 } 3 among is { { 1 2
3 } }, whereas Eric's word must compute the combinations
