阿克曼函数（Ackerman）是非原始递归函数的例子；它需要两个自然数作为输入值，输出一个自然数。它的输出值增长速度非常高，仅是(4,3)的输出已大得不能准确计算。

　　Ackerman函数定义如下:

　　若m=0 返回n+1

　　若m>0且n=0 返回Ackerman(m-1,1)

　　若m>0且n>0 返回Ackerman(m-1,Ackerman(m,n-1))

-Ackermann function (Ackerman) examples of non-primitive recursive function　it takes two natural numbers as input, output a natural number. Its output value growth rate is very high, only (4,3) output has been so large that can not be accurately calculated. Ackerman function is defined as follows: If m = 0 return n+1 if m>　0 and n = 0 return Ackerman (m-1, 1) if m>　0 and n>　0 return Ackerman (m-1, Ackerman (m, n-1))