[Tcl-bugs] [ tcl-Feature Requests-793779 ] Include source files only once

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Feature Requests item #793779, was opened at 2003-08-23 16:58
Message generated for change (Tracker Item Submitted) made by Item Submitter
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Category: 18. Commands M-Z
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Markus Elfring (elfring)
Assigned to: Donal K. Fellows (dkf)
Summary: Include source files only once

Initial Comment:
Multiple inclusion of source files can be avoided in compiled 
programming languages like C++ by preprocessor 
statements.
...
#if 
!defined(_my_text_included)
#include 
"my_text.h"
#endif
...

The TCL function 
"source" includes files, too. But there are no preprocessor 
directives in a scripting language like TCL. Their statements get 
executed every time.
The language PHP provides the 
function "http://de.php.net/manual/en/function.include-
once.php".

I suggest to add the option "-once" to avoid 
multiple inclusions of TCL code.

...
if 
{_my_text_included == 0} \
 {
  source "my_text.h"
 
}
...
# Write just one line to achieve the same as before 
with more safety
source -once "my_text.h"

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