Are there differences between //, / * * / and #?

Question

Are there differences between //, / * * / and #?

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#1 by (17 votes)

12

Considering how important it is to comment on a code , that question came to me.

I noticed that there are several ways to comment lines / parts of the code :

//
/* */
#

Example:

// comentando uma linha

/* comentando
   um intervalo
   do código */

# comentando uma linha

Questions:

Are there other ways to comment?
Excluding these settings from the example, are there more differences between them ?

php

asked by anonymous 08.08.2018 / 21:54

1 answer

Is Android an OS or software stack? What is the function of the operators, and in Javascript

score 17 · Accepted Answer

The essential thing is this:

The // and # are identical in terms of operation;
The // and /* are completely different in terms of operation, and each has a specific usage scenario:

The // or # are for line comments . Everything that comes after them is ignored until there is a line break.

Already, /* is a block comment that can end: 1) before the end of the line; or 2) online other than where it started. In both cases what determines the end of the comment is the sequence */ ;
You have a third situation, __halt_compiler , which is not comment , but also causes the code to be ignored from that point forward (can be used to "ignore" a longer comment, or even have a special function for reuse of the source file).

No more differences.

Notes:

You can not nest block comments.
```
/* abc /* 123 */ def */
```
In the case above, the def is no longer commented, it will give error. The first */ is worth it. (The fact is that the second /* is ignored).

It has a technique to "key" comments of block very curious, that is this (credits to the comment section of PHP):

When you define a block like this, simply modify a slash so that it is "worth" or not:

//*
    Bloco "chaveável" com várias linhas.
    Em princípio, são duas linhas com "comment de linha"
    Basta modificar UMA barra, que vira um "comment de bloco"
// */

Excluding only the first slash:

/*
    Bloco "chaveável" com várias linhas.
    Em princípio, são duas linhas com "comment de linha"
    Basta modificar UMA barra, que vira um "comment de bloco"
// */

It has a type of comment that is used in documentation tools (not part of the language itself) which is /** . In practice it is a regular block comment /* followed by an asterisk (although, a special token for that case was adopted in parser , T_DOC_COMMENT ).

For more details, see this post:

What's the difference between "/ *" and "/ **" comments in PHP?
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