proc(n) 						       Tcl Built-In Commands							   proc(n)

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NAME

       proc - Create a Tcl procedure

SYNOPSIS

       proc name args body
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DESCRIPTION

       The  proc  command  creates  a  new Tcl procedure named name, replacing any existing command or procedure there may have been by that name.
       Whenever the new command is invoked, the contents of body will be executed by the Tcl interpreter.  Normally, name is unqualified (does not
       include the names of any containing namespaces), and the new procedure is created in the current namespace.  If name includes any namespace
       qualifiers, the procedure is created in the specified namespace.  Args specifies the formal arguments to the procedure.	It consists  of  a
       list, possibly empty, each of whose elements specifies one argument.  Each argument specifier is also a list with either one or two fields.
       If there is only a single field in the specifier then it is the name of the argument; if there are two fields, then the first is the  argu-
       ment  name and the second is its default value.	Arguments with default values that are followed by non-defaulted arguments become required
       arguments.  In 8.6 this will be considered an error.

       When name is invoked a local variable will be created for each of the formal arguments to the procedure; its value will	be  the  value	of
       corresponding argument in the invoking command or the argument's default value.	Actual arguments are assigned to formal arguments strictly
       in order.  Arguments with default values need not be specified in a procedure invocation.  However, there must be enough  actual  arguments
       for  all  the  formal arguments that do not have defaults, and there must not be any extra actual arguments.  Arguments with default values
       that are followed by non-defaulted arguments become required arguments (in 8.6 it will be considered an error).	There is one special  case
       to  permit  procedures with variable numbers of arguments.  If the last formal argument has the name args, then a call to the procedure may
       contain more actual arguments than the procedure has formals.  In this case, all of the actual arguments starting at the one that would	be
       assigned  to  args  are	combined into a list (as if the list command had been used); this combined value is assigned to the local variable
       args.

       When body is being executed, variable names normally refer to local variables, which are created automatically when referenced and  deleted
       when  the  procedure returns.  One local variable is automatically created for each of the procedure's arguments.  Other variables can only
       be accessed by invoking one of the global, variable, upvar or namespace upvar commands.

       The proc command returns an empty string.  When a procedure is invoked, the procedure's return value is the value  specified  in  a  return
       command.  If the procedure does not execute an explicit return, then its return value is the value of the last command executed in the pro-
       cedure's body.  If an error occurs while executing the procedure body, then the procedure-as-a-whole will return that same error.

EXAMPLES

       This is a procedure that accepts arbitrarily many arguments and prints them out, one by one.
	      proc printArguments args {
		 foreach arg $args {
		    puts $arg
		 }
	      }

       This procedure is a bit like the incr command, except it multiplies the contents of the named variable by the value, which defaults to 2:
	      proc mult {varName {multiplier 2}} {
		 upvar 1 $varName var
		 set var [expr {$var * $multiplier}]
	      }

SEE ALSO

       info(n), unknown(n)

KEYWORDS

       argument, procedure

Tcl																	   proc(n)