高阶函数

<?php  
$twice_learnfk=function($f, $v) { 
   return $f($f($v)); 
};  

$f=function($v) { 
   return $v + 3; 
}; 

echo($twice_learnfk($f, 7));

def twice(function): 
   return lambda x: function(function(x))  
def f(x): 
   return x + 3 
g=twice(f)
print g(7)