FilterError returns err, unless errors.Is(err, i) returns true for any i in ignore, in which case it returns nil.

LiftErrorFunc takes any 1-arity function "f(x) => error", and returns a new function that takes an additional error input.

MustMap is used to construct a map if it is nil, or return the input unchanged (i.e.

Reserve grows a slice, if necessary, to fit at least size extra elements.

SetLength grows a slice, if necessary, so that has a capacity of at least size elements, and a length of exactly size elements.

WrapBlock word-wraps a whitespace-delimited string to a given number of columns.