Function prefixScanWithFunc [src]

Same as prefixScan, but with a user-provided, mathematically associative function.

Prototype

 pub fn prefixScanWithFunc( comptime hop: isize, vec: anytype, comptime ErrorType: type, comptime func: fn (@TypeOf(vec), @TypeOf(vec)) if (ErrorType == void) @TypeOf(vec) else ErrorType!@TypeOf(vec), comptime identity: std.meta.Child(@TypeOf(vec)), ) if (ErrorType == void) @TypeOf(vec) else ErrorType!@TypeOf(vec)

Parameters

hop: isize

ErrorType: typeThe error type that func might return. Set this to void if func doesn't return an error union.

func: fn (@TypeOf(vec), @TypeOf(vec)) if (ErrorType == void) @TypeOf(vec) else ErrorType!@TypeOf(vec)

identity: std.meta.Child(@TypeOf(vec))When one operand of the operation performed by func is this value, the result must equal the other operand.
For example, this should be 0 for addition or 1 for multiplication.

Source

  pub fn prefixScanWithFunc(
    comptime hop: isize,
    vec: anytype,
    /// The error type that `func` might return. Set this to `void` if `func` doesn't return an error union.
    comptime ErrorType: type,
    comptime func: fn (@TypeOf(vec), @TypeOf(vec)) if (ErrorType == void) @TypeOf(vec) else ErrorType!@TypeOf(vec),
    /// When one operand of the operation performed by `func` is this value, the result must equal the other operand.
    /// For example, this should be 0 for addition or 1 for multiplication.
    comptime identity: std.meta.Child(@TypeOf(vec)),
) if (ErrorType == void) @TypeOf(vec) else ErrorType!@TypeOf(vec) {
    // I haven't debugged this, but it might be a cousin of sorts to what's going on with interlace.
    if (builtin.cpu.arch.isMIPS()) @compileError("TODO: Find out why prefixScan doesn't work on MIPS");

    const len = vectorLength(@TypeOf(vec));

    if (hop == 0) @compileError("hop can not be 0; you'd be going nowhere forever!");
    const abs_hop = if (hop < 0) -hop else hop;

    var acc = vec;
    comptime var i = 0;
    inline while ((abs_hop << i) < len) : (i += 1) {
        const shifted = if (hop < 0) shiftElementsLeft(acc, abs_hop << i, identity) else shiftElementsRight(acc, abs_hop << i, identity);

        acc = if (ErrorType == void) func(acc, shifted) else try func(acc, shifted);
    }
    return acc;
}  