Version 0 of static data in command procedures

Updated 2004-10-04 17:35:14

Tcl offers several techniques that can be used to implement static data in command procedures. This page is intended to present the pros and cons.

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Example:

Here is a command procedure for a simple Tcl command that makes use of a "static" value. Roughly, it's a constant value that each invocation of the command will use without changing, but a value that need not be created at all if the command is never evaluated.

  int
  OneObjCommand(
    ClientData cd,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const objv[]
  )
  {
    Tcl_SetObjResult(interp, Tcl_NewIntObj(1));
    return TCL_OK;
  }

  Tcl_CreateObjCommand(interp, "one", OneObjCommand,
    NULL, NULL);