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shl

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

math.shl

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

File

lib/std/math.zig:598

Code

pub fn shl(comptime T: type, a: T, shift_amt: anytype) T {
    const is_shl = shift_amt >= 0;
    const abs_shift_amt = @abs(shift_amt);
    const casted_shift_amt = casted_shift_amt: switch (@typeInfo(T)) {
        .int => |info| {
            if (abs_shift_amt < info.bits) break :casted_shift_amt @as(
                Log2Int(T),
                @intCast(abs_shift_amt),
            );
            if (info.signedness == .unsigned or is_shl) return 0;
            return a >> (info.bits - 1);
        },
        .vector => |info| {
            const Child = info.child;
            const child_info = @typeInfo(Child).int;
            if (abs_shift_amt < child_info.bits) break :casted_shift_amt @as(
                @Vector(info.len, Log2Int(Child)),
                @splat(@as(Log2Int(Child), @intCast(abs_shift_amt))),
            );
            if (child_info.signedness == .unsigned or is_shl) return @splat(0);
            return a >> @splat(child_info.bits - 1);
        },
        else => comptime unreachable,
    };
    return if (is_shl) a << casted_shift_amt else a >> casted_shift_amt;
}