Hi,
Is there a good standard implementation of Bresenham's linedraw? My silly
attempt, which is basically just a translation of a Processing program, is
below. I know it can be done better than this, I'm just not sure how - and
this program fails to compile with a rather bizarre error related to the
first unless statement which apparently takes something like 5 inputs!?
Mark
! Create a new 10x10 grid
: newgrid ( n n -- byte-array ) * <byte-array> ;
! Get address of cell x,y
: celladdress ( n n -- n ) 10 * + ;
! Get value of cell at x,y
: cellat ( byte-array n n -- n ) celladdress swap nth ;
! Do operation on cell at x,y
:: docell ( array x y op -- ) x y celladdress array op change-nth ;
! Set value of cell at x,y
:: setcell ( array x y val -- ) array x y [ drop val ] docell ;
:: los ( map ax ay bx by -- bool )
bx ax - abs :> dx!
by ay - abs :> dy!
dx! dy! - :> err!
t :> continue!
t :> result!
ax ay
[ continue! ] [
2dup cellat 0 = [ f :> continue! f :> result! ] unless
2dup by = swap bx = and [ f :> continue! t :> result! ] when
err 2 *
dup 0 dy! - > [ err! dy! - :> err! roll dx! sgn + -roll ] when
dx! < [ err! dx! + :> err! dy! sgn + ] when
] while
result! ;
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