fixed jslint errors, spacing a bit

bools.js

'use strict';

var not = function (x) {
    if (x) {
        return false;
    }
    return true;
};

var and = function (a, b) {
    if (a) {
        if (b) {
            return true;
        }
        return false;
    }
    return false;
};

var or = function (a, b) {
    if (a) {
        return true;
    }
    if (b) {
        return true;
    }
    return false;
};

lists.js

'use strict';
/*global is_zero, inc, dec, sub, zero*/

var empty_list = function (selector) {
    return selector(undefined, undefined, true);
};

var prepend = function (el, list) {
    return function (selector) {
        return selector(el, list, false);
    };
};

var head = function (list) {
    return list(function (h, t, e) {
        return h;
    });
};

var tail = function (list) {
    return list(function (h, t, e) {
        return t;
    });
};

var is_empty = function (list) {
    return list(function (h, t, e) {
        return e;
    });
};

var map = function (fn, l) {
    if (is_empty(l)) {
        return empty_list;
    }
    return prepend(fn(head(l)), map(fn, tail(l)));
};

var filter = function (fn, l) {
    if (is_empty(l)) {
        return empty_list;
    }
    if (fn(head(l))) {
        return prepend(head(l), filter(fn, tail(l)));
    }
    return filter(fn, tail(l));
};

var nth = function (l, n) {
    if (is_zero(n)) {
        return head(l);
    }
    return nth(tail(l), dec(n));
};

var drop = function (l, n) {
    if (is_zero(n)) {
        return l;
    }
    return drop(tail(l), dec(n));
};

var take = function (l, n) {
    if (is_zero(n)) {
        return empty_list;
    }
    return prepend(head(l), take(tail(l), dec(n)));
};

var slice = function (l, start, end) {
    return take(drop(l, start), sub(end, start));
};

var length = function (l) {
    if (is_empty(l)) {
        return zero;
    }
    return inc(length(tail(l)));
};

numbers.js

'use strict';
/*global empty_list, prepend, head, tail, is_empty, and, or, not*/

var zero = empty_list;

var inc = function (n) {
    return prepend(empty_list, n);
};

var dec = function (n) {
    return tail(n);
};

var one = inc(zero);

var is_zero = function (n) {
    return is_empty(n);
};

var add = function (a, b) {
    if (is_zero(b)) {
        return a;
    }
    return add(inc(a), dec(b));
};

var sub = function (a, b) {
    if (is_zero(b)) {
        return a;
    }
    return add(dec(a), dec(b));
};

var mul = function (a, b) {
    if (is_zero(b)) {
        return zero;
    }
    return add(a, mul(a, dec(b)));
};

var pow = function (a, b) {
    if (is_zero(b)) {
        return one;
    }
    return mul(a, pow(a, dec(b)));
};

var is_equal = function (n, m) {
    if (and(is_zero(n), is_zero(m))) {
        return true;
    }
    if (or(is_zero(n), is_zero(m))) {
        return false;
    }
    return is_equal(dec(n), dec(m));
};

var less_than = function (a, b) {
    if (and(is_zero(a), is_zero(b))) {
        return false;
    }

    if (is_zero(a)) {
        return true;
    }

    if (is_zero(b)) {
        return false;
    }
    return less_than(dec(a), dec(b));
};

var greater_than = function (a, b) {
    return less_than(b, a);
};

var div = function (a, b) {
    if (less_than(a, b)) {
        return zero;
    }
    return inc(div(sub(a, b), b));
};

var rem = function (a, b) {
    if (less_than(a, b)) {
        return a;
    }
    return rem(sub(a, b), b);
};