如何在C中的for(;;)循环中初始化几个变量? [英] How do I initialize several variables in a for (;;) loop in C?

问题描述

我以为可以在for循环中初始化几个变量:

I thought one could initialize several variables in a for loop:

for (int i = 0, char* ptr = bam; i < 10; i++) { ... }

但是我刚刚发现这是不可能的. GCC出现以下错误:

But I just found out that this is not possible. GCC gives the following error:

错误:"char"之前的预期unqualified-id

error: expected unqualified-id before 'char'

真的不能在for循环中初始化不同类型的变量吗?

Is it really true that you can't initialize variables of different types in a for loop?

推荐答案

您可以(但通常不应该)使用本地结构类型.

You can (but generally shouldn't) use a local struct type.

for ( struct { int i; char* ptr; } loopy = { 0, bam };
      loopy.i < 10 && * loopy.ptr != 0;
      ++ loopy.i, ++ loopy.ptr )
    { ... }

---

从C ++ 11开始，只要不依赖局部变量，就可以更优雅地初始化各个部分:

---

Since C++11, you can initialize the individual parts more elegantly, as long as they don't depend on a local variable:

for ( struct { int i = 0; std::string status; } loop;
      loop.status != "done"; ++ loop.i )
    { ... }

这几乎足以使人真正使用它.

This is just almost readable enough to really use.

C ++ 17计划解决结构化绑定的问题:

C++17 is scheduled to address the problem with structured bindings:

for ( auto [ i, status ] = { 0, ""s }; status != "done"; ++ i )

但是，详细的功能集和语法仍在不断变化.

However, the detailed feature set and syntax are still in flux.

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