New: Array Lib

[joshcox]

Terms encompass the data type of values that can be used within the microKanren system. Here's what they are:

export type Term = boolean | undefined | null | number | string | symbol | Array<any>;

Note that the Array term type is congruous to the List (pairs, cons cells, etc) type used in classic microKanren implementations. However, the data pattern (how to construct/deconstruct) Arrays in JavaScript isn't congruous with List implementations; they're not cons cells. Consider the following implementation of pusho; intuitive structural composition doesn't work to unify an array and therefore extra information may need to be passed to unify so that we may represent subsets of an array as symbols.

const pusho = (arr: Term, item: Term, out: Term): Goal => {
    if (typeof arr === "symbol") {
        // return unify([arr, Symbol.for("spread-left"), item], out);
    }
    if (Array.isArray(arr)) return unify([...arr, item], out);

    return fail(`pusho :: rest term type (${typeof arr}) not supported`);
}