pokecrystal-board/engine/routines/getsquareroot.asm
2017-12-29 18:53:21 +01:00

31 lines
480 B
NASM

GetSquareRoot: ; 13b87
; Return the square root of de in b.
; Rather than calculating the result, we take the index of the
; first value in a table of squares that isn't lower than de.
ld hl, .Squares
ld b, 0
.loop
; Make sure we don't go past the end of the table.
inc b
ld a, b
cp $ff
ret z
; Iterate over the table until b**2 >= de.
ld a, [hli]
sub e
ld a, [hli]
sbc d
jr c, .loop
ret
.Squares: ; 13b98
root = 1
rept $ff
dw root * root
root = root + 1
endr