Merge pull request #3315 from ziglang/mv-std-lib

Move std/ to lib/std/

1 files changed, 50 insertions, 0 deletions

diff --git a/lib/std/math/signbit.zig b/lib/std/math/signbit.zig
new file mode 100644
index 0000000000..e5c5909292
--- /dev/null
+++ b/lib/std/math/signbit.zig
@@ -0,0 +1,50 @@
+const std = @import("../std.zig");
+const math = std.math;
+const expect = std.testing.expect;
+
+/// Returns whether x is negative or negative 0.
+pub fn signbit(x: var) bool {
+    const T = @typeOf(x);
+    return switch (T) {
+        f16 => signbit16(x),
+        f32 => signbit32(x),
+        f64 => signbit64(x),
+        else => @compileError("signbit not implemented for " ++ @typeName(T)),
+    };
+}
+
+fn signbit16(x: f16) bool {
+    const bits = @bitCast(u16, x);
+    return bits >> 15 != 0;
+}
+
+fn signbit32(x: f32) bool {
+    const bits = @bitCast(u32, x);
+    return bits >> 31 != 0;
+}
+
+fn signbit64(x: f64) bool {
+    const bits = @bitCast(u64, x);
+    return bits >> 63 != 0;
+}
+
+test "math.signbit" {
+    expect(signbit(f16(4.0)) == signbit16(4.0));
+    expect(signbit(f32(4.0)) == signbit32(4.0));
+    expect(signbit(f64(4.0)) == signbit64(4.0));
+}
+
+test "math.signbit16" {
+    expect(!signbit16(4.0));
+    expect(signbit16(-3.0));
+}
+
+test "math.signbit32" {
+    expect(!signbit32(4.0));
+    expect(signbit32(-3.0));
+}
+
+test "math.signbit64" {
+    expect(!signbit64(4.0));
+    expect(signbit64(-3.0));
+}