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std.math.cast handles signed integers

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Andrew Kelley 2018-03-27 15:20:07 -04:00
parent 6cb99fdac3
commit 5b00dee0c2
1 changed files with 15 additions and 2 deletions
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17
std/math/index.zig
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@ -515,15 +515,28 @@ test "math.negateCast" {
/// Cast an integer to a different integer type. If the value doesn't fit,
/// return an error.
pub fn cast(comptime T: type, x: var) !T {
pub fn cast(comptime T: type, x: var) (error{Overflow}!T) {
comptime assert(@typeId(T) == builtin.TypeId.Int); // must pass an integer
if (x > @maxValue(T)) {
comptime assert(@typeId(@typeOf(x)) == builtin.TypeId.Int); // must pass an integer
if (@maxValue(@typeOf(x)) > @maxValue(T) and x > @maxValue(T)) {
return error.Overflow;
} else if (@minValue(@typeOf(x)) < @minValue(T) and x < @minValue(T)) {
return error.Overflow;
} else {
return T(x);
}
}
test "math.cast" {
if (cast(u8, u32(300))) |_| @panic("fail") else |err| assert(err == error.Overflow);
if (cast(i8, i32(-200))) |_| @panic("fail") else |err| assert(err == error.Overflow);
if (cast(u8, i8(-1))) |_| @panic("fail") else |err| assert(err == error.Overflow);
if (cast(u64, i8(-1))) |_| @panic("fail") else |err| assert(err == error.Overflow);
assert((try cast(u8, u32(255))) == u8(255));
assert(@typeOf(try cast(u8, u32(255))) == u8);
}
pub fn floorPowerOfTwo(comptime T: type, value: T) T {
var x = value;