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std.math: Add least common multiple (lcm)

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oittaa 2025-03-24 16:07:40 +01:00 • committed by GitHub
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2
lib/std/math.zig
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@ -235,6 +235,7 @@ pub const sinh = @import("math/sinh.zig").sinh;
pub const cosh = @import("math/cosh.zig").cosh; pub const cosh = @import("math/cosh.zig").cosh;
pub const tanh = @import("math/tanh.zig").tanh; pub const tanh = @import("math/tanh.zig").tanh;
pub const gcd = @import("math/gcd.zig").gcd; pub const gcd = @import("math/gcd.zig").gcd;
pub const lcm = @import("math/lcm.zig").lcm;
pub const gamma = @import("math/gamma.zig").gamma; pub const gamma = @import("math/gamma.zig").gamma;
pub const lgamma = @import("math/gamma.zig").lgamma; pub const lgamma = @import("math/gamma.zig").lgamma;
@ -395,6 +396,7 @@ test {
_ = cosh; _ = cosh;
_ = tanh; _ = tanh;
_ = gcd; _ = gcd;
_ = lcm;
_ = gamma; _ = gamma;
_ = lgamma; _ = lgamma;

29
lib/std/math/lcm.zig Normal file
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@ -0,0 +1,29 @@
//! Least common multiple (https://mathworld.wolfram.com/LeastCommonMultiple.html)
const std = @import("std");
/// Returns the least common multiple (LCM) of two integers (`a` and `b`).
/// For example, the LCM of `8` and `12` is `24`, that is, `lcm(8, 12) == 24`.
/// If any of the arguments is zero, then the returned value is 0.
pub fn lcm(a: anytype, b: anytype) @TypeOf(a, b) {
// Behavior from C++ and Python
// If an argument is zero, then the returned value is 0.
if (a == 0 or b == 0) return 0;
return @abs(b) * (@abs(a) / std.math.gcd(@abs(a), @abs(b)));
}
test lcm {
const expectEqual = std.testing.expectEqual;
try expectEqual(lcm(0, 0), 0);
try expectEqual(lcm(1, 0), 0);
try expectEqual(lcm(-1, 0), 0);
try expectEqual(lcm(0, 1), 0);
try expectEqual(lcm(0, -1), 0);
try expectEqual(lcm(7, 1), 7);
try expectEqual(lcm(7, -1), 7);
try expectEqual(lcm(8, 12), 24);
try expectEqual(lcm(-23, 15), 345);
try expectEqual(lcm(120, 84), 840);
try expectEqual(lcm(84, -120), 840);
try expectEqual(lcm(1216342683557601535506311712, 436522681849110124616458784), 16592536571065866494401400422922201534178938447014944);
}