tailcall - Replace the current procedure with another command
tailcall command ?arg ...?
tailcall(1t) Tcl Built-In Commands tailcall(1t)
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NAME
tailcall - Replace the current procedure with another command
SYNOPSIS
tailcall command ?arg ...?
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DESCRIPTION
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.
EXAMPLE
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]
}
}
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/tcl-8 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
SEE ALSO
apply(n), proc(n), uplevel(n)
KEYWORDS
call, recursion, tail recursion
NOTES
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from http://prdownloads.sourceforge.net/tcl/tcl-
core8.6.7-src.tar.gz.
Further information about this software can be found on the open source
community website at https://www.tcl.tk/.
Tcl 8.6 tailcall(1t)