Function cast [src]

Cast an integer to a different integer type. If the value doesn't fit, return null.

Prototype

pub fn cast(comptime T: type, x: anytype) ?T

Parameters

T: type

Example

 test cast {
    try testing.expect(cast(u8, 300) == null);
    try testing.expect(cast(u8, @as(u32, 300)) == null);
    try testing.expect(cast(i8, -200) == null);
    try testing.expect(cast(i8, @as(i32, -200)) == null);
    try testing.expect(cast(u8, -1) == null);
    try testing.expect(cast(u8, @as(i8, -1)) == null);
    try testing.expect(cast(u64, -1) == null);
    try testing.expect(cast(u64, @as(i8, -1)) == null);

    try testing.expect(cast(u8, 255).? == @as(u8, 255));
    try testing.expect(cast(u8, @as(u32, 255)).? == @as(u8, 255));
    try testing.expect(@TypeOf(cast(u8, 255).?) == u8);
    try testing.expect(@TypeOf(cast(u8, @as(u32, 255)).?) == u8);
}

Source

  pub fn cast(comptime T: type, x: anytype) ?T {
    comptime assert(@typeInfo(T) == .int); // must pass an integer
    const is_comptime = @TypeOf(x) == comptime_int;
    comptime assert(is_comptime or @typeInfo(@TypeOf(x)) == .int); // must pass an integer
    if ((is_comptime or maxInt(@TypeOf(x)) > maxInt(T)) and x > maxInt(T)) {
        return null;
    } else if ((is_comptime or minInt(@TypeOf(x)) < minInt(T)) and x < minInt(T)) {
        return null;
    } else {
        return @as(T, @intCast(x));
    }
}  