[[General meaning in software]]





[[much used in Tcl]]

In Tcl, to ''enhance'' a core command (or existing proc) by renaming the command to be enhanced, then creating a procedure with the same name as the core command that provides the desired functionality.

Easy example, provided by [RS]:

    rename exit _exit

    proc exit {{code 0}} {
        set fp [open test a]
        puts $fp "trapped exit at [clock format [clock seconds]]"
        _exit $code
    }

General case needs [uplevel], as in
         uplevel 1 [linsert $args 0 _original_PROC]
or, with 8.5,
         uplevel 1 [list _original_PROC {expand}$args]
 ...

See [stacking].

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[Category Development]