有条件的初始化是如何处理的，是它一个很好的做法？ [英] How is conditional initialization handled and is it a good practice?

问题描述

我尝试几种可能的做法之间作出选择。比方说，我的功能的数，如果（）块，对数据的工作，这是唯一的它们。

• 我应该声明和初始化本地（为块）的块中的数据？这是否有运行时性能成本（由于在堆栈中分配运行时）？




• 或者我应该声明和/或初始化在函数入口的所有变量，所以这是在一个做的，可能是速度更快，操作块？




• 或者我应该单独在不同的功能，如果（）块，即使他们是一对夫妇只排长队的，只有在程序中使用吗？

还是我ovelooking另外，清洁，选择吗？是个问题，即使在它的电流，一般形式回答的？

解决方案

  

我应该声明和初始化本地（该块）的数据块中？

绝对：这往往使程序的可读性。

。

  

这是否有运行时性能成本（由于在堆栈中分配运行时）？

没有：所有分配完成前期 - 堆栈中的空间保留给在输入函数的所有分支的变量，而不是输入分支时。此外，这甚至可以为您节省一些空间，因为在非重叠枝分配给变量的空间可被编译器重复使用。

  

或者我应该声明和/或初始化在函数入口的所有变量，所以这是在一个做的，可能是速度更快，操作块？

没有，这不是更快，并且可以稍微浪费。

  

或者我应该单独在不同的功能，如果（）块，即使他们是一对夫妇只排长队的，只有在程序中使用呢？

这很可能会对你的程序可读性产生负面影响。

I am trying to decide between several possible practices. Say, my function has a number of if() blocks, that work on data, that is unique to them.

• Should I declare and initialize the local (for the block) data inside the block? Does this have runtime performance cost (due to runtime allocation in the stack)?

• Or should I declare and/or initialize all variables at function entry, so that is is done in one, possibly faster, operation block?

• Or should I seperate the if() blocks in different functions, even though they are only a couple of lines long and used only one in the program?

Or am I ovelooking another, cleaner, option? Is the question even answerable in it's current, general form?

解决方案

Should I declare and initialize the local (for the block) data inside the block?

Absolutely: this tends to make programs more readable.

Does this have runtime performance cost (due to runtime allocation in the stack)?

No: all allocations are done upfront - the space on the stack is reserved for variables in all branches upon entering a function, not when the branch is entered. Moreover, this could even save you some space, because the space allocated for variables in non-overlapping branches can be reused by the compiler.

Or should I declare and/or initialize all variables at function entry, so that is is done in one, possibly faster, operation block?

No, this is not faster, and could be slightly more wasteful.

Or should I seperate the if() blocks in different functions, even though they are only a couple of lines long and used only one in the program?

That would probably have a negative impact on readability of your program.

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