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Diffstat (limited to 'engine/math/getsquareroot.asm')
| -rw-r--r-- | engine/math/getsquareroot.asm | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/engine/math/getsquareroot.asm b/engine/math/getsquareroot.asm new file mode 100644 index 000000000..412fd04ff --- /dev/null +++ b/engine/math/getsquareroot.asm @@ -0,0 +1,32 @@ +NUM_SQUARE_ROOTS EQU 255 + +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 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: ; 13b98 +x = 1 +rept NUM_SQUARE_ROOTS + dw x * x +x = x + 1 +endr |