70 lines
1.9 KiB
Plaintext
70 lines
1.9 KiB
Plaintext
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'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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.TH tailcall n 8.6 Tcl "Tcl Built-In Commands"
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.so man.macros
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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tailcall \- Replace the current procedure with another command
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.SH SYNOPSIS
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\fBtailcall \fIcommand\fR ?\fIarg ...\fR?
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.BE
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.SH DESCRIPTION
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.PP
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The \fBtailcall\fR command replaces the currently executing procedure, lambda
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application, or method with another command. The \fIcommand\fR, which will
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have \fIarg ...\fR passed as arguments if they are supplied, will be looked up
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in the current namespace context, not in the caller's. Apart from that
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difference in resolution, it is equivalent to:
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.PP
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.CS
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return [uplevel 1 [list \fIcommand\fR ?\fIarg ...\fR?]]
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.CE
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.PP
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This command may not be invoked from within an \fBuplevel\fR into a procedure
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or inside a \fBcatch\fR inside a procedure or lambda.
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'\" TODO: sort out the mess with the [try] command!
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.SH EXAMPLE
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.PP
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Compute the factorial of a number.
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.PP
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.CS
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proc factorial {n {accum 1}} {
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if {$n < 2} {
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return $accum
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}
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\fBtailcall\fR factorial [expr {$n - 1}] [expr {$accum * $n}]
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}
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.CE
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.PP
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Print the elements of a list with alternating lines having different
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indentations.
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.PP
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.CS
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proc printList {theList} {
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if {[llength $theList]} {
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puts "> [lindex $theList 0]"
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\fBtailcall\fR printList2 [lrange $theList 1 end]
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}
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}
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proc printList2 {theList} {
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if {[llength $theList]} {
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puts "< [lindex $theList 0]"
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\fBtailcall\fR printList [lrange $theList 1 end]
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}
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}
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.CE
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.SH "SEE ALSO"
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apply(n), proc(n), uplevel(n)
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.SH KEYWORDS
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call, recursion, tail recursion
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'\" Local Variables:
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'\" mode: nroff
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'\" fill-column: 78
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'\" End:
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