functional.jinx

-- Implementation of higher order functions in jinx
library functional

-- transform a collection with a user supplied function
function transformed {coll} with {fun}
    set result to []
    loop x over coll
        set result[x key] to (call fun with x value)
    end
    return result
end

------
The `then` at the end allows chaining
by stopping the next function in the chain from having precedence over the last argument (fun)
------
function {coll} transformed (with) {fun} then
    return transformed coll with fun
end

-- filter a collection by a user supplied predicate
function filtered {coll} by {predicate}
    set result to []
    loop x over coll
        if (call predicate with x value)
            set result[x key] to x value
        end
    end
    return result
end

-- filter for chaining
function {coll} filtered (by) {predicate} then
    return filtered coll by predicate
end

-- reduce a collection to a single value by applying a binary function
function reduced {coll} by {binary_fun} starting with {initial value}
    set current to initial value
    loop x over coll
        set current to (call binary_fun with current, x value)
    end
    return current
end

-- reduce
function {coll} reduced (by) {binary fun}
    return reduced coll by binary fun starting with 0
end