NAME
  proc - Create a Tcl procedure 

SYNOPSIS
  proc name args body

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 argument name and the second
  is its default value.

  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. 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 don't have defaults, and there must not be
  any extra actual arguments. 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. Global variables can only be
  accessed by invoking the global command or the upvar command. Namespace
  variables can only be accessed by invoking the variable command or the
  upvar command.

  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 doesn't execute an explicit return, then its return
  value is the value of the last command executed in the procedure's body.
  If an error occurs while executing the procedure body, then the
  procedure-as-a-whole will return that same error.

EXAMPLE
  % proc product {x y} {
    expr $x * $y
  }
  
  % product 5 5
  25
  
  % product 20 99
  1980
  
  % product 7
  no value given for parameter "y" to "product"


  % proc fac n {
      if {$n <= 1} {
        return 1
      }
      expr $n * [fac [expr $n - 1]]
    }
    
  % fac 7
  5040
  
  % fac 6
  720
  
  % fac 0
  1


  % set x 5
  5
  
  % set y 10
  10
  
  % proc noArgs {} {
      global x y
      puts "x = $x"
      puts "y = $y"
    }
  
  % proc myinc {val {inc 1}} {
      expr $val + $inc
    }

  % noArgs
  x = 5
  y = 10
  
  % myinc 7
  29
  
  % proc sum {base args} {
      set s $base
      foreach i $args {
        incr s $i
      }
      return $s
    }
    
  % sum 5 1 2 3 4 5
  20
  
  % sum 0 1 2 3
  6

SEE ALSO
  none