Re: Back & Forth - Co-routines

Ruvim <ruvim.pinka@gmail.com> wrote:

An artificial example:

While wondering down roads less taken, I took a path where
bacForth CUT: and -CUT were used in lieu of CATCH THROW .


( ENTER is the same as ';:' )
: LOCAL ( x adr -- )
    r> -rot dup @ over 2>r ! ENTER 2r> ! ;

\ prefixed '-' to indicate this word does a cut
: -idiv ( n1 n2\0 -- n3 |  n1 0 -- true )
  dup if /
    else 2drop true -CUT
    then
;

: ?idiv ( n1 n2 -- n1/n2 false | <nothing> )
  CUT: -idiv ." Valid: " false      
;

42 variable a
42 variable b

: ?/ ( u1 u2 -- u1/u2 )
  a local b local
  b @ a @ ?idiv
  if ." Bogus! " 666 then .
;

i. 100 5 ?/ --> Valid: 20
i. a ? b ? --> 42 42
i. 100 0 ?/ --> Bogus! 666
i. a ? b ? --> 42 42

forget ?/

: ?/ ( u1 u2 -- u1/u2 )
  a local b local
  b @ a @ ' ?idiv ENTER 
  if ." Bogus! " 666 then .
;

i. 100 5 ?/ --> Valid: 20
i. a ? b ? --> 42 42
i. 100 0 ?/ --> Bogus! 666
i. a ? b ? --> 42 42

forget ?/

: ?/ ( u1 u2 -- u1/u2 )
  a local b local
  b @ a @ (: cut: -idiv ." Valid: " false ;) ENTER
  if ." Bogus! " 666 then .
;

i. 100 5 ?/ --> Valid: 20
i. a ? b ? --> 42 42
i. 100 0 ?/ --> Bogus! 666
i. a ? b ? --> 42 42

+echo
-fin-