Add math library

This covers the majority of the functions as covered by the C99
specification for a math library.

Code is adapted primarily from musl libc, with the pow and standard
trigonometric functions adapted from the Go stdlib.

Changes:

 - Remove assert expose in index and import as needed.
 - Add float log function and merge with existing base 2 integer
   implementation.

See https://github.com/tiehuis/zig-fmath.
See #374.

1 files changed, 30 insertions, 0 deletions

diff --git a/std/math/isfinite.zig b/std/math/isfinite.zig
new file mode 100644
index 0000000000..a820cb2f52
--- /dev/null
+++ b/std/math/isfinite.zig
@@ -0,0 +1,30 @@
+const math = @import("index.zig");
+const assert = @import("../debug.zig").assert;
+
+pub fn isFinite(x: var) -> bool {
+    const T = @typeOf(x);
+    switch (T) {
+        f32 => {
+            const bits = @bitCast(u32, x);
+            bits & 0x7FFFFFFF < 0x7F800000
+        },
+        f64 => {
+            const bits = @bitCast(u64, x);
+            bits & (@maxValue(u64) >> 1) < (0x7FF << 52)
+        },
+        else => {
+            @compileError("isFinite not implemented for " ++ @typeName(T));
+        },
+    }
+}
+
+test "isFinite" {
+    assert(isFinite(f32(0.0)));
+    assert(isFinite(f32(-0.0)));
+    assert(isFinite(f64(0.0)));
+    assert(isFinite(f64(-0.0)));
+    assert(!isFinite(math.inf(f32)));
+    assert(!isFinite(-math.inf(f32)));
+    assert(!isFinite(math.inf(f64)));
+    assert(!isFinite(-math.inf(f64)));
+}