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ActiveTcl User Guide |
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tailcall - Replace the current procedure with another command
tailcall command ?arg ...?
The tailcall command replaces the currently executing
procedure, lambda application, or method with another command. The
command, which will have arg ... passed as arguments
if they are supplied, will be looked up in the current namespace
context, not in the caller's. Apart from that difference in
resolution, it is equivalent to:
return [uplevel 1 [list command ?arg ...?]]
This command may not be invoked from within an uplevel into a procedure or inside
a catch inside a procedure
or lambda.
Compute the factorial of a number.
proc factorial {n {accum 1}} {
if {$n < 2} {
return $accum
}
tailcall factorial [expr {$n - 1}] [expr {$accum * $n}]
}
Print the elements of a list with alternating lines having
different indentations.
proc printList {theList} {
if {[llength $theList]} {
puts "> [lindex $theList 0]"
tailcall printList2 [lrange $theList 1 end]
}
}
proc printList2 {theList} {
if {[llength $theList]} {
puts "< [lindex $theList 0]"
tailcall printList [lrange $theList 1 end]
}
}
apply, proc, uplevel
call, recursion, tail recursion
Copyright © 1995-1997 Roger E. Critchlow Jr.
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.