[http://stackoverflow.com/questions/14579920/fast-sign-of-integer-in-c](http://forum.nim-lang.org///stackoverflow.com/questions/14579920/fast-sign-of-integer-in-c)
I would like to have a sign function in std lib.
I was really surprised that the brachless variant makes such a difference -- I
had expected nearly no difference because result dominated by random()
function, or due to identical assembler code of gcc 5.4.0.
import random
#proc sign(x: int): int =
# if (x > 0): return 1
# elif (x < 0): return -1
# else: return 0
proc sign(x: int): int =
(x > 0).int - (x < 0).int
#proc sign(x: float): int =
# if (x > 0): return 1
# elif (x < 0): return -1
# else: return 0
proc sign(x: float): int =
(x > 0).int - (x < 0).int
var j = 0
for i in 0 .. 1e7.int:
j += sign(random(7).float - 3.0)
echo j
j = 0
for i in 0 .. 1e7.int:
j += sign(random(7) - 3)
echo j
stefan@nuc ~/sign $ nim c -d:release s.nim
stefan@nuc ~/sign $ time ./s
-2839
855
real 0m0.314s
user 0m0.312s
sys 0m0.000s
stefan@nuc ~/sign $ nim c -d:release s.nim
stefan@nuc ~/sign $ time ./s
-2839
855
real 0m0.188s
user 0m0.188s
sys 0m0.000s
