The lazy evaluation feature is needed to handle recursive data structures like trees and graphs 懒惰求值的特性常用在处理像tree或者graph这样的递归数据结构上。
One example of a lazy evaluation is a function that generates an infinite list of fibonacci numbers, but where the computation of the 一个懒惰计算的例子是生成无穷fibonacci列表的函数,但是对第n个
In lazy evaluation, an expression is not evaluated as soon as it is bound to a variable, but when the evaluator is forced to produce the expression s value 在懒惰计算中,表达式不是在绑定到变量时立即计算,而是在求值程序需要产生表达式的值时进行计算。