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I have an ada program that has a main procedure, now I want to add another procedure but I got an error saying "end of file expected, file can have only one compilation unit". I did some looking an I think it is because you can only have 1 procedure per file. Do I have to create another file and put the procedure alone in that? If so how would I compile both the codes and run it? Can someone show me how I would be able to compile both and run the whole file together.

sashoalm
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Dennis Garfield
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    possible duplicate of [Ada beginner Stack program](http://stackoverflow.com/questions/16182824/ada-beginner-stack-program) – Simon Wright Feb 20 '15 at 16:31
  • Simon's comment is bang on. But if one procedure calls the other, you can simply declare the other local to the first (i.e. in its declaration region) –  Feb 20 '15 at 16:57
  • What would the declaration syntax look like? Would I have to name the file? – Dennis Garfield Feb 20 '15 at 17:01
  • The answer to the question "how would I compile both the codes and run it" depends on what compiler you're using. I assume you're using GNAT, but if not please let us know what compiler you're using. – ajb Feb 21 '15 at 21:29

3 Answers3

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As the compiler says, you can only have one compilation unit per file. A main program is compilation unit, which is a procedure.

If you want one program to run two procedures which both are compilation units, when you can do it like this:

with One_Procedure,
     Another_Procedure;
procedure Sequential is
begin
   One_Procedure;
   Another_Procedure;
end Sequential;

If you want to run the two procedures in parallel do it like this:

with One_Procedure,
     Another_Procedure;
procedure Parallel is
   task One;
   task Another;

   task body One is
   begin
      One_Procedure;
   end One;

   task body Another is
   begin
      Another_Procedure;
   end Another;
begin
   null;
end Parallel;

The procedures may of course also be declared in the declarative region of the main program or in some packages.

Jacob Sparre Andersen
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    Note that "only one compilation unit per file" is **not** an Ada rule. It's a GNAT restriction. Not all Ada compilers have this restriction. – ajb Feb 21 '15 at 21:26
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Both recent GNATs and GPRbuild have options for indicating which units of a file you want compiled: that's -gnateINNN for gcc, and -eInn for gprbuild, as documented here.

Another option is to become familiar with gnatchop for extracting compilation units from files, and with -m for minimal recompilation; the latter prevents having to compile the world only because of running gnatchop when an edit has not "semantically" touched all compilation units in a file. GNAT then ignores time stamps. I sometimes run commands like

gnatchop -r -w -c allofit.ada && gnatmake -Ptest -m someunit.adb

where someunit.adb is generated for compilation unit Someunit (a procedure, a package) contained in file allofit.ada.

B98
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You can have 1 main procedure but several procedures within main procedure.

procedure main is
    ...text...

    procedure sub1 () is
    begin
        ...text...
    end sub1;

    procedure sub2 () is
    begin
        ...text...
    end sub2;

    ...text...
end main;
Jacob
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