Function lossyCast [src]

Cast a value to a different type. If the value doesn't fit in, or can't be perfectly represented by, the new type, it will be converted to the closest possible representation.

Prototype

pub fn lossyCast(comptime T: type, value: anytype) T

Parameters

T: type

Example

 test lossyCast {
    try testing.expect(lossyCast(i16, 70000.0) == @as(i16, 32767));
    try testing.expect(lossyCast(u32, @as(i16, -255)) == @as(u32, 0));
    try testing.expect(lossyCast(i9, @as(u32, 200)) == @as(i9, 200));
    try testing.expect(lossyCast(u32, @as(f32, @floatFromInt(maxInt(u32)))) == maxInt(u32));
    try testing.expect(lossyCast(u32, nan(f32)) == 0);
}

Source

  pub fn lossyCast(comptime T: type, value: anytype) T {
    switch (@typeInfo(T)) {
        .float => {
            switch (@typeInfo(@TypeOf(value))) {
                .int => return @floatFromInt(value),
                .float => return @floatCast(value),
                .comptime_int => return value,
                .comptime_float => return value,
                else => @compileError("bad type"),
            }
        },
        .int => {
            switch (@typeInfo(@TypeOf(value))) {
                .int, .comptime_int => {
                    if (value >= maxInt(T)) {
                        return maxInt(T);
                    } else if (value <= minInt(T)) {
                        return minInt(T);
                    } else {
                        return @intCast(value);
                    }
                },
                .float, .comptime_float => {
                    // In extreme cases, we probably need a language enhancement to be able to
                    // specify a rounding mode here to prevent `@intFromFloat` panics.
                    const max: @TypeOf(value) = @floatFromInt(maxInt(T));
                    const min: @TypeOf(value) = @floatFromInt(minInt(T));
                    if (isNan(value)) {
                        return 0;
                    } else if (value >= max) {
                        return maxInt(T);
                    } else if (value <= min) {
                        return minInt(T);
                    } else {
                        return @intFromFloat(value);
                    }
                },
                else => @compileError("bad type"),
            }
        },
        else => @compileError("bad result type"),
    }
}  