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std.math.sign: Narrow integer return types to possible values #23595

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std.math.sign: Narrow integer return types to possible values #23595

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14 changes: 12 additions & 2 deletions lib/std/math.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1762,12 +1762,22 @@ pub const F80 = struct {
}
};

// Named `Signum` since `Sign` is already taken.
fn Signum(T: type) type {
return switch (@typeInfo(T)) {
.int => |int| IntFittingRange(if (int.signedness == .signed) -1 else 0, 1),
.vector => |vec| @Vector(vec.len, Signum(vec.child)),
else => T,
};
}

/// Returns -1, 0, or 1.
/// Supports integer and float types and vectors of integer and float types.
/// Unsigned integer types will always return 0 or 1.
/// Returned integer types are narrowed to fit the possible values.
/// Branchless.
pub inline fn sign(i: anytype) @TypeOf(i) {
const T = @TypeOf(i);
pub inline fn sign(i: anytype) Signum(@TypeOf(i)) {
const T = Signum(@TypeOf(i));
return switch (@typeInfo(T)) {
.int, .comptime_int => @as(T, @intFromBool(i > 0)) - @as(T, @intFromBool(i < 0)),
.float, .comptime_float => @as(T, @floatFromInt(@intFromBool(i > 0))) - @as(T, @floatFromInt(@intFromBool(i < 0))),
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