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, 89 insertions, 0 deletions

diff --git a/std/math/ceil.zig b/std/math/ceil.zig
new file mode 100644
index 0000000000..f80e493f1f
--- /dev/null
+++ b/std/math/ceil.zig
@@ -0,0 +1,89 @@
+const builtin = @import("builtin");
+const math = @import("index.zig");
+const assert = @import("../debug.zig").assert;
+
+pub fn ceil(x: var) -> @typeOf(x) {
+    const T = @typeOf(x);
+    switch (T) {
+        f32 => @inlineCall(ceil32, x),
+        f64 => @inlineCall(ceil64, x),
+        else => @compileError("ceil not implemented for " ++ @typeName(T)),
+    }
+}
+
+fn ceil32(x: f32) -> f32 {
+    var u = @bitCast(u32, x);
+    var e = i32((u >> 23) & 0xFF) - 0x7F;
+    var m: u32 = undefined;
+
+    if (e >= 23) {
+        return x;
+    }
+    else if (e >= 0) {
+        m = 0x007FFFFF >> u32(e);
+        if (u & m == 0) {
+            return x;
+        }
+        math.forceEval(x + 0x1.0p120);
+        if (u >> 31 == 0) {
+            u += m;
+        }
+        u &= ~m;
+        @bitCast(f32, u)
+    } else {
+        math.forceEval(x + 0x1.0p120);
+        if (u >> 31 != 0) {
+            return -0.0;
+        } else {
+            1.0
+        }
+    }
+}
+
+fn ceil64(x: f64) -> f64 {
+    const u = @bitCast(u64, x);
+    const e = (u >> 52) & 0x7FF;
+    var y: f64 = undefined;
+
+    if (e >= 0x3FF+52 or x == 0) {
+        return x;
+    }
+
+    if (u >> 63 != 0) {
+        @setFloatMode(this, builtin.FloatMode.Strict);
+        y = x - math.f64_toint + math.f64_toint - x;
+    } else {
+        @setFloatMode(this, builtin.FloatMode.Strict);
+        y = x + math.f64_toint - math.f64_toint - x;
+    }
+
+    if (e <= 0x3FF-1) {
+        math.forceEval(y);
+        if (u >> 63 != 0) {
+            return -0.0;    // Compiler requires return.
+        } else {
+            1.0
+        }
+    } else if (y < 0) {
+        x + y + 1
+    } else {
+        x + y
+    }
+}
+
+test "ceil" {
+    assert(ceil(f32(0.0)) == ceil32(0.0));
+    assert(ceil(f64(0.0)) == ceil64(0.0));
+}
+
+test "ceil32" {
+    assert(ceil32(1.3) == 2.0);
+    assert(ceil32(-1.3) == -1.0);
+    assert(ceil32(0.2) == 1.0);
+}
+
+test "ceil64" {
+    assert(ceil64(1.3) == 2.0);
+    assert(ceil64(-1.3) == -1.0);
+    assert(ceil64(0.2) == 1.0);
+}