Function shl [src]

Shifts left. Overflowed bits are truncated. A negative shift amount results in a right shift.

Prototype

pub fn shl(comptime T: type, a: T, shift_amt: anytype) T

Parameters

T: typea: T

Example

 test shl {
    try testing.expect(shl(u8, 0b11111111, @as(usize, 3)) == 0b11111000);
    try testing.expect(shl(u8, 0b11111111, @as(usize, 8)) == 0);
    try testing.expect(shl(u8, 0b11111111, @as(usize, 9)) == 0);
    try testing.expect(shl(u8, 0b11111111, @as(isize, -2)) == 0b00111111);
    try testing.expect(shl(u8, 0b11111111, 3) == 0b11111000);
    try testing.expect(shl(u8, 0b11111111, 8) == 0);
    try testing.expect(shl(u8, 0b11111111, 9) == 0);
    try testing.expect(shl(u8, 0b11111111, -2) == 0b00111111);
    try testing.expect(shl(@Vector(1, u32), @Vector(1, u32){42}, @as(usize, 1))[0] == @as(u32, 42) << 1);
    try testing.expect(shl(@Vector(1, u32), @Vector(1, u32){42}, @as(isize, -1))[0] == @as(u32, 42) >> 1);
    try testing.expect(shl(@Vector(1, u32), @Vector(1, u32){42}, 33)[0] == 0);
}

Source

  pub fn shl(comptime T: type, a: T, shift_amt: anytype) T {
    const abs_shift_amt = @abs(shift_amt);

    const casted_shift_amt = blk: {
        if (@typeInfo(T) == .vector) {
            const C = @typeInfo(T).vector.child;
            const len = @typeInfo(T).vector.len;
            if (abs_shift_amt >= @typeInfo(C).int.bits) return @splat(0);
            break :blk @as(@Vector(len, Log2Int(C)), @splat(@as(Log2Int(C), @intCast(abs_shift_amt))));
        } else {
            if (abs_shift_amt >= @typeInfo(T).int.bits) return 0;
            break :blk @as(Log2Int(T), @intCast(abs_shift_amt));
        }
    };

    if (@TypeOf(shift_amt) == comptime_int or @typeInfo(@TypeOf(shift_amt)).int.signedness == .signed) {
        if (shift_amt < 0) {
            return a >> casted_shift_amt;
        }
    }

    return a << casted_shift_amt;
}  