67 lines
3.7 KiB
HTML
67 lines
3.7 KiB
HTML
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<HTML><HEAD><TITLE>Built-In Commands - proc manual page</TITLE></HEAD><BODY>
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<H3><A NAME="M2">NAME</A></H3>
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proc - Create a Tcl procedure
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>proc </B><I>name args body</I><BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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The <B>proc</B> command creates a new Tcl procedure named
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<I>name</I>, replacing
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any existing command or procedure there may have been by that name.
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Whenever the new command is invoked, the contents of <I>body</I> will
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be executed by the Tcl interpreter.
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Normally, <I>name</I> is unqualified
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(does not include the names of any containing namespaces),
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and the new procedure is created in the current namespace.
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If <I>name</I> includes any namespace qualifiers,
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the procedure is created in the specified namespace.
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<I>Args</I> specifies the formal arguments to the
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procedure. It consists of a list, possibly empty, each of whose
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elements specifies
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one argument. Each argument specifier is also a list with either
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one or two fields. If there is only a single field in the specifier
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then it is the name of the argument; if there are two fields, then
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the first is the argument name and the second is its default value.
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<P>
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When <I>name</I> is invoked a local variable
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will be created for each of the formal arguments to the procedure; its
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value will be the value of corresponding argument in the invoking command
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or the argument's default value.
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Arguments with default values need not be
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specified in a procedure invocation. However, there must be enough
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actual arguments for all the
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formal arguments that don't have defaults, and there must not be any extra
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actual arguments. There is one special case to permit procedures with
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variable numbers of arguments. If the last formal argument has the name
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<B>args</B>, then a call to the procedure may contain more actual arguments
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than the procedure has formals. In this case, all of the actual arguments
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starting at the one that would be assigned to <B>args</B> are combined into
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a list (as if the <B><A HREF="../TkCmd/list.htm">list</A></B> command had been used); this combined value
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is assigned to the local variable <B>args</B>.
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<P>
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When <I>body</I> is being executed, variable names normally refer to
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local variables, which are created automatically when referenced and
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deleted when the procedure returns. One local variable is automatically
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created for each of the procedure's arguments.
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Global variables can only be accessed by invoking
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the <B><A HREF="../TkCmd/global.htm">global</A></B> command or the <B><A HREF="../TkCmd/upvar.htm">upvar</A></B> command.
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Namespace variables can only be accessed by invoking
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the <B><A HREF="../TkCmd/variable.htm">variable</A></B> command or the <B><A HREF="../TkCmd/upvar.htm">upvar</A></B> command.
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<P>
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The <B>proc</B> command returns an empty string. When a procedure is
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invoked, the procedure's return value is the value specified in a
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<B><A HREF="../TkCmd/return.htm">return</A></B> command. If the procedure doesn't execute an explicit
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<B><A HREF="../TkCmd/return.htm">return</A></B>, then its return value is the value of the last command
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executed in the procedure's body.
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If an error occurs while executing the procedure
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body, then the procedure-as-a-whole will return that same error.
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<H3><A NAME="M5">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/info.htm">info</A></B>, <B><A HREF="../TkCmd/unknown.htm">unknown</A></B>
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<H3><A NAME="M6">KEYWORDS</A></H3>
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<A href="../Keywords/A.htm#argument">argument</A>, <A href="../Keywords/P.htm#procedure">procedure</A>
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<HR><PRE>
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<A HREF="../copyright.htm">Copyright</A> © 1993 The Regents of the University of California.
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<A HREF="../copyright.htm">Copyright</A> © 1994-1996 Sun Microsystems, Inc.
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<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
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</BODY></HTML>
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