highorder-functions for php 5.3 and higher with simple datastore example

example.php

<?php
include_once("highorderfuncs.php");

/*
 * simple datastore example
 */
$createDefaultItem = function($key){
  return (object)array("title" => $key);
};

$set = function($store,$key,$value){
  $store->$key = $value;
};

$get = function($store,$key){
  return isset($store->$key) ? $store->$key : false;
};

/*
 * highorder functions using curry 
 */
$store        = (object)array();
$getFromStore = curry( $get,$store);
$saveToStore  = curry( $set,$store);

$saveToStore("foo","bar");
print_r( $getFromStore("foo") );

/*
 * highorder functions using compose (piping)
 */
$getDefaultItemAndSave = compose( $createDefaultItem, curry( $saveToStore, time() ) );
$getOrCreateItem       = either( $getFromStore, $getDefaultItemAndSave );   
print_r( $getOrCreateItem("newitem") );
print_r( $store );        

highorderfuncs.php

<?php
/* high order functions utils for php */

// curry!
// example: $arrayToLines = curry( implode, "\n" ); 
//          $arrayToLines( ["one","two"] );
function curry($fn, $arg, $obj = null) {
    return function() use ($fn, $arg, $obj) {
        $args = func_get_args();
        array_unshift($args, $arg);
        if($obj) {
            $fn = array($obj, $fn);
        }
        return call_user_func_array($fn, $args);
    };
}

// This function allows creating a new function from two functions passed into it
function compose(&$f, &$g) {
  // Return the composed function
  return function() use($f,$g) {
    // Get the arguments passed into the new function
    $x = func_get_args();
    // Call the function to be composed with the arguments
    // and pass the result into the first function.
    return $f(call_user_func_array($g, $x));
  };
}
// Convenience wrapper for mapping
function map(&$data, &$f) {
  return array_map($f, $data);
}
// Convenience wrapper for filtering arrays
function filter(&$data, &$f) {
  return array_filter($data, $f);
}
// Convenience wrapper for reducing arrays
function fold(&$data, &$f) {
  return array_reduce($data, $f);
}

function either($a,$b){
  return function($c) use($a,$b) { $a($c) || $b($c); };
};