curry with placeholders curry2 and curry3

gistfile1.js

function curry2(fn) {
    return function(a, b) {
        switch (arguments.length) {
        case 1:
            return function(B) {
                return fn(a, B);
            };
        default:
            if (a === __) {
                return function(A) {
                    return fn(A, b);
                };
            }
            return fn(a, b);
        }
    };
}

function curry3(fn) {
    return function(a, b, c) {
        switch (arguments.length) {
        case 1:
            return curry2(function(B, C) {
                return fn(a, B, C);
            });
        case 2:
            if (a === __) {
                return curry2(function(A, C) {
                    return fn(A, b, C);
                });
            }
            return function(C) {
                return fn(a, b, C);
            };
        default:
            if (a === __ && b === __) {
                return curry2(function(A, B) {
                    return fn(A, B, c);
                });
            }
            else if (a === __) {
                return function(A) {
                    return fn(A, b, c);
                };
            }
            else if (b === __) {
                return function(B) {
                    return fn(a, B, c);
                };
            }
            return fn(a, b, c);
        }
    }
}