list-out-of-lambda.js

"use strict";

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 (head, tail, e) {
    return head;
  });
}

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

var is_empty = function (list) {
  return list(function(head, tail, empty) {
    return empty;
  });
}

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

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

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

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

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

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

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

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

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

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

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

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

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

var less_than = function(a, b) {
    if (and(is_zero(a), is_zero(b))) {
        return false;
    } else if (is_zero(a)) {
        return true;
    } else if (is_zero(b)) {
        return false;
    } else {
        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;
    } else {
        return inc(div(sub(a, b), b));
    }
};

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

var nth = function(list, number) {
    if (is_zero(number)) {
        return head(list);
    } else {
        return nth(tail(list), dec(number));
    }
};

var drop = function(list, number) {
    if (is_zero(number)) {
        return list;
    } else {
        return drop(tail(list), dec(number));
    }
};

var take = function(list, number) {
    if (is_zero(number)) {
        return empty_list;
    } else {
        return prepend(head(list), take(tail(list), dec(number)));
    }
};

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

var zero = empty_list;

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


var concat = function(a, b) {
  if(is_empty(a)) {
    return b;
  }
  return concat(take(a, dec(length(a))), prepend(head(drop(a, dec(length(a)))), b));
};

var append = function (el, list) {
  if (is_empty(list)) {
    return prepend(el, list);
  }  
  return concat(list, prepend(el, empty_list));
}

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

var remove = function (list) {
  return filter(function (el) { return el; }, list);
}
var contains_number = function (number, list) {
  if (is_empty(list)) {
    return false;
  } else if (is_equal(number, head(list))) {
    return true;
  } else {
    return contains_number(number, tail(list));
  }
}

var dump = function (list) {
  var arr = [];
  while (false === is_empty(list)) {
    arr.push(head(list));
    list = tail(list);
  }
  console.log(arr);
}