标准的ml循环麻烦 [英] Standard ml loop troubles

问题描述

我正在设置一个函数，该函数将模拟循环直到满足条件为止.

I am setting up a function that will simulate a loop until a condition is met.

我的总体计划是使用递归，但是我试图先降低基础知识.

My overall plan is to use recursion but I am trying to get the basics down first.

我有一个使用If语句的基本函数，该语句查看X的值是什么.我打算使用递归将X用作计数器，但稍后我会介绍.

I got a basic function working using an If statement that is seeing what the value of X is. I plan to use recursion to use X as an counter but I will get to that later.

我现在主要关心的是，似乎我只能在"then"语句之后执行1条命令.

My main concern right now is, it seems I can only do 1 command after the "then" statement.

fun whileloop (x,a) =
    if (x<4)
    then a+1 
    else a;

因此，此功能可以正常工作，但似乎我唯一可以执行的命令是a + 1.如果之后我尝试执行其他任何命令，则在else ...之前失败.

So this function works perfectly fine, but it seems the only command I can do is the a+1. If I try to perform any other command after that, before the else...it fails.

例如，以下代码将对我失败.

For example, the below code will fail on me.

fun whileloop (x,a) =
    if (x<4)
    then a+1 
    print "Testing"
    else a;

我的最终目标是创建一个循环，该循环将反复执行多个动作，直到X达到零为止.我需要使用不同的功能执行类似5-6的操作.

my ultimate goal is to create a loop that will perform several actions over and over until X reaches zero. I need to perform like 5-6 actions using different functions.

推荐答案

您可以使用分号运算符按顺序求值多个表达式:

You can evaluate several expressions in sequence using the semicolon operator:

( e1; e2; ...; eN )

例如，

fun iter n f = if n = 0 then () else (f n; iter (n-1) f)

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