什么是 Perl 内置运算符/函数? [英] What are Perl built-in operators/functions?

问题描述

我正在阅读 Simon 的Beginning PerlCozens 和在第 8 章 - 子程序中他指出子程序"是用户函数，而 print、open、split> 等是内置的运算符或函数.

I'm reading Beginning Perl by Simon Cozens and in Chapter 8 - Subroutines he states that "subroutines" are user functions, while print, open, split, etc. are built-in operators or functions.

它们是什么?它们真的是内置的、语言内在的特性(比如 C 的 sizeof 运算符)还是它们实际上是 main 模块的子例程/函数?

What are they? Are they really built-in, language-intrinsic features (like C's sizeof operator) or are they, actually, subroutines/functions of the main module?

如果它们是子例程，while、for、unless 等是否也是子例程?+、-、eq等操作符怎么样?

If they're subroutines, are while, for, unless, etc. also subroutines? What about the operators like +, -, eq, etc.?

推荐答案

print, open, split 不是子程序.它们不会导致子调用.它们甚至不存在于符号表中(在 main:: 或其他地方，尽管您可以将它们称为 CORE::split 等)，并且无法获得对他们代码的引用(尽管在 CORE:: 中正在为他们创建代理子程序，以便您将它们视为子程序时).它们就像 + 一样是运算符.

print, open, split are not subroutines. They do not result in sub calls. They are not even present in the symbol table (in main:: or otherwise, although you can refer to them as CORE::split, etc), and one cannot get a reference to their code (although work is being done to create proxy subs for them in CORE:: for when you want to treat them as subroutines). They are operators just like +.

$ perl -MO=Concise,-exec -e'sub f {} f()'
1  <0> enter 
2  <;> nextstate(main 2 -e:1) v:{
3  <0> pushmark s
4  <#> gv[*f] s
5  <1> entersub[t3] vKS/TARG,1      <--- sub call
6  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'split /;/'
1  <0> enter 
2  <;> nextstate(main 1 -e:1) v:{
3  </> pushre(/";"/) s/64
4  <#> gvsv[*_] s
5  <$> const[IV 0] s
6  <@> split[t2] vK                 <--- not a sub call
7  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'$x + $y'
1  <0> enter 
2  <;> nextstate(main 1 -e:1) v:{
3  <#> gvsv[*x] s
4  <#> gvsv[*y] s
5  <2> add[t3] vK/2                 <--- Just like this
6  <@> leave[1 ref] vKP/REFC
-e syntax OK

它们有多种名称:

• 内置函数
• 功能
• 内置函数
• 命名运算符

大多数都被认为是以下之一:

And most are considered to be one of the following:

• 列表运算符
• 命名一元运算符

子程序通常被称为函数(就像在 C 和 C++ 中一样)，因此函数"是一个含糊不清的词.这种歧义似乎是您提出问题的基础.

Subroutines are often called functions (as they are in C and C++), so "function" is an ambiguous word. This ambiguity appears to be the basis of your question.

对于while、for、unless等，都是流程控制语句使用的关键字

while (f()) { g() }

和语句修饰符

g() while f();

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