server/www/fun.js

function Fun() {
  return {
    defaultCompare: defaultCompare,
    insert: insert,
    map: map,
    mapFilter: mapFilter,
    isSet: isSet,
    of: of,
    proj: proj
  };

  function insert(obj, t, compare, min, max) {
    min = min == undefined ? 0 : min;
    max = max == undefined ? t.length : max;
    compare = compare == undefined ? defaultCompare : compare;
    if(max - min < 1) {
      return min;
    }
    var avg = Math.floor((max + min) / 2);
    if (compare(obj, t[avg]) < 0) {
      return insert(obj, t, compare, min, avg);
    } else {
      return insert(obj, t, compare, avg+1, max);
    }
  }

  function defaultCompare(a, b) {
    if(a < b) {
      return -1;
    } else if(a > b) {
      return 1;
    } else {
      return 0;
    }
  }

  function map(mapper, f) {
    return function() {
      var args = Array.prototype.map.call(arguments, mapper);
      return f.apply(null, args);
    }
  }

  function of(o) {
    return function(key) {return o[key];};
  }

  function proj(key) {
    return function(o) {return o[key];};
  }

  function mapFilter(mapper, predicate) {
    return function(array) {
      return array.reduce(function(accumulator, elem) {
        var v = mapper(elem);
        return predicate(v) ? accumulator.concat(v) : accumulator;
      }, []);
    };
  }

  function isSet(x) {
    return x != undefined;
  }
}