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authormid-kid <esteve.varela@gmail.com>2018-04-04 22:26:07 +0200
committermid-kid <esteve.varela@gmail.com>2018-04-04 22:26:07 +0200
commitd3cc861d334c8b773c1b6c662ed9924c43cef009 (patch)
tree0e8df3581a081f77167785502c093fbfc5535d73 /engine/math/get_square_root.asm
parent81fff9bb80af3db0ee381c824261b8963e1cc221 (diff)
Fix snake_case filenames
Renamed a bunch of files, most of them one-off functions, to better fit the general snake_case naming scheme. Also renamed some awfully long filenames.
Diffstat (limited to 'engine/math/get_square_root.asm')
-rw-r--r--engine/math/get_square_root.asm32
1 files changed, 32 insertions, 0 deletions
diff --git a/engine/math/get_square_root.asm b/engine/math/get_square_root.asm
new file mode 100644
index 000000000..412fd04ff
--- /dev/null
+++ b/engine/math/get_square_root.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