pokecrystal/engine/math/get_square_root.asm

31 lines
491 B
NASM

NUM_SQUARE_ROOTS EQU 255
GetSquareRoot:
; 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 NUM_SQUARE_ROOTS
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:
for x, 1, NUM_SQUARE_ROOTS + 1
dw x**2
endr