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digitalmars.D.learn - Declare and Define Before Use? [rant]

reply kdevel <kdevel vogtner.de> writes:
Why are people writing

    import std.stdio;

    void main ()
    {
       S s;
       s.foo;
    }

    struct S {
       void foo ()
       {
          writeln ("a");
       }
    }

but not

    void main ()
    {
       S s;
       s.foo;
    }

    struct S {
       void foo ()
       {
          writeln ("a");
       }
    }

    import std.stdio;

?
Apr 04 2018
parent reply Ali <fakeemail example.com> writes:
On Wednesday, 4 April 2018 at 18:57:27 UTC, kdevel wrote:

 Why are people writing

    import std.stdio;

    void main ()
    {



    }

    struct S {



    }

 but not

    void main ()
    {



    }

    struct S {



    }

    import std.stdio;

 ?



Personally i found it weird and inconsistent that
you can import and define anywhere at module scope
but for any other scope you have to define and import before use

I think the rules should have been the same everywhere
and if there was an exception to be made, it could be made for 
the main function
since the main function is special anyway

Personally I would either do

 import



 declare and define



 main


or

 main



 import



 declare and define


the later, is because main is special, so it is as if i am saying
this is what i want to do (main) and to do it (import) this stuff 
and (declare and define this stuff) ... putting main first would 
be just to highlight it and attract attention to it

importing and declaring anywhere at module scope is just too 
random for my taste
Apr 04 2018
parent reply kdevel <kdevel vogtner.de> writes:
On Wednesday, 4 April 2018 at 19:19:30 UTC, Ali wrote:

 On Wednesday, 4 April 2018 at 18:57:27 UTC, kdevel wrote:
 [...]
 I think the rules should have been the same everywhere
 and if there was an exception to be made, it could be made for 
 the main function
 since the main function is special anyway


The main function of a program corresponds to the final paragraph 
of a novel. I never understood why programmers place this 
function which possibly depends on all other functions in the 
translation unit at the beginning.

BTW: You can't write

    void main ()
    {
       x.writeln;
       int x;
    }
    import std.stdio;

There is no reason why the declaration of x should not be 
postponed.
Apr 04 2018
next sibling parent reply Ali <fakeemail example.com> writes:
On Wednesday, 4 April 2018 at 19:51:27 UTC, kdevel wrote:

 On Wednesday, 4 April 2018 at 19:19:30 UTC, Ali wrote:
 BTW: You can't write

    void main ()
    {
       x.writeln;
       int x;
    }
    import std.stdio;


This is because x is not module scope
you can do this

    void main ()
    {
       x.writeln;

    }

    import std.stdio;
    int x;
Apr 04 2018
parent Rubn <where is.this> writes:
On Wednesday, 4 April 2018 at 20:01:55 UTC, Ali wrote:

 On Wednesday, 4 April 2018 at 19:51:27 UTC, kdevel wrote:

 On Wednesday, 4 April 2018 at 19:19:30 UTC, Ali wrote:
 BTW: You can't write

    void main ()
    {
       x.writeln;
       int x;
    }
    import std.stdio;


 This is because x is not module scope
 you can do this

    void main ()
    {
       x.writeln;

    }

    import std.stdio;
    int x;


Cause there's no scope at the module level.


struct A
{
     A* a;

     ~this()
     {
         // use a
     }
}

void main()
{
     A b = A(&a);
     A a; // in this case "a" destructed before "b", but "b" uses 
"a"

}


Destruction and order of destruction becomes much more confusing. 
You also can't do scope(exit) at the module level for a reason. 
This mess shouldn't be allowed, it just makes it way worse to 
understand what is going on.
Apr 04 2018
prev sibling parent Cym13 <cpicard openmailbox.org> writes:
On Wednesday, 4 April 2018 at 19:51:27 UTC, kdevel wrote:

 On Wednesday, 4 April 2018 at 19:19:30 UTC, Ali wrote:

 On Wednesday, 4 April 2018 at 18:57:27 UTC, kdevel wrote:
 [...]
 I think the rules should have been the same everywhere
 and if there was an exception to be made, it could be made for 
 the main function
 since the main function is special anyway


 The main function of a program corresponds to the final 
 paragraph of a novel. I never understood why programmers place 
 this function which possibly depends on all other functions in 
 the translation unit at the beginning.

 BTW: You can't write

    void main ()
    {
       x.writeln;
       int x;
    }
    import std.stdio;

 There is no reason why the declaration of x should not be 
 postponed.


I've never seen the main function at the top but I think it would 
be be nice place for it honnestly. Sounds more like a C legacy 
than anything.

The reason why I place common imports at the top is because I 
read a *lot* of code as my day job is to audit software. While 
skimming rapidly through directories looking only at the top of 
each file I know what they are about and can quickly infer their 
purpose based solely on imports. This file does IO, this one web 
stuff, etc (and to debunk quickly a counter argument I've heard 
before: no, given how convoluted file names quickly get 
especially in languages like java, directory structure isn't 
nearly enough).

The same is true for the main function. If your code is clean it 
should the main is the place where you orchestrate the whole 
program. You should be able to grasp most of the program flow 
from it. What it setups, information flow, etc. Of course in 
practice people are often trying to burry useful information deep 
down in functions (where it's generally too coupled for its own 
good, but that's another story). Such burrying makes it harder to 
get useful information from the main function, hence maybe why so 
many are comfortable putting it at the end (I know I do by habit).

On the other hand, if the main effectively describes the programs 
course then putting it at the beggining makes complete sense: it 
is what you want to see first to get an idea of what the program 
is doing. No function could be better suited for that.

Some points hinted here make me think of 
https://www.youtube.com/watch?v=FyCYva9DhsI so maybe it could be 
of some interest to you.
Apr 04 2018