Question about speed

[MortenB]

I wonder if there is any difference between procedural calls and function calls in Free Pascal.
The basic idea is that I will parse through a huge text of 300k, and record positions of various key elements in this text.
Thousands of positions will be stored in "MyResult", and I believe I should make a Pointer to this variable, and use the pointer as a procedure parameter.
But... does it really matter? Maybe the compiler does this automatically anyway?
Are there any speed preferences as to how this should be handled?

As a function:
MyResult := ParseTheText(SourceText);

As a procedural call:
ParseTheText(SourceText,MyResult);
–––
Function ParseTheText(Const SourceText:AnsiString):MyType;

OR

Procedure ParseTheText(Const SourceText:AnsiString; MyResult: MyType);

[ASerge]

Procedure ParseTheText(Const SourceText:AnsiString; MyResult: MyType);

I assume you mean "; var MyResult: MyType"?
Answer: no difference. For functions that have a structured or managed type result, the compiler generates a procedure, passing the result with the last parameter as var.

Sometimes a form with the "out" parameter is more descriptive.

Code: Pascal  [Select][+][-]

1. procedure ParseTheText(const SourceText: AnsiString; out MyResult: MyType);

[MortenB]

Thank you ASerge

Even a bonus. I was not aware of the "out" parameter. Great! It for sure makes it more descriptive.
But then again. I do prefer the Function, if that provides the same speed.

I just thought that doing it as a function might make two variables.
Ie... first the function fills up the "Result"-variable of the chosen type.
       Then the "Result"-variable is copied into MyResult.

My idea was to use a pointer, so that the function or procedure skips a temporary variable, and writes directly to the target variable.
As I understand you, this might be exactly what the compiler does anyway?

[ASerge]

I just thought that doing it as a function might make two variables.
Ie... first the function fills up the "Result"-variable of the chosen type.
       Then the "Result"-variable is copied into MyResult.

Yes, it is. So using a procedure instead of a function will allow you to do this micro-optimization. Example: use the SysUtils FmtStr function instead of the Format function.

Sometimes the functional form is safer if the variable is used incorrectly: for example, it is first modified, and then used as if without modification.
Example: this code does not work correctly in Delphi (even in version 10.3), but it works correctly in FPC.

Code: Pascal  [Select][+][-]

1. {$APPTYPE CONSOLE}
2. {$IFDEF FPC}
3.   {$MODE OBJFPC}
4.   {$LONGSTRINGS ON}
5. {$ENDIF}
6.  
7. uses
8.   SysUtils;
9.  
10. var
11.   S: string;
12. begin
13.   S := StringOfChar('1', 4096);
14.   S := Format('1:%s+%:0s', [S]);
15.   Writeln(S);
16.   S := StringOfChar('2', 4096);
17.   FmtStr(S, '2:%s+%:0s', [S]);
18.   Writeln(S);
19.   Readln;
20. end.