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# tree.tcl --
#
# Implementation of a tree data structure for Tcl.
#
# Copyright (c) 1998-2000 by Ajuba Solutions.
#
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
# RCS: @(#) $Id: tree.tcl,v 1.45 2009/06/22 18:21:59 andreas_kupries Exp $
# @mdgen EXCLUDE: tree_c.tcl
package require Tcl 8.2
package require struct::list
namespace eval ::struct::tree {}
# ### ### ### ######### ######### #########
## Management of tree implementations.
# ::struct::tree::LoadAccelerator --
#
# Loads a named implementation, if possible.
#
# Arguments:
# key Name of the implementation to load.
#
# Results:
# A boolean flag. True if the implementation
# was successfully loaded; and False otherwise.
proc ::struct::tree::LoadAccelerator {key} {
variable accel
set r 0
switch -exact -- $key {
critcl {
# Critcl implementation of tree requires Tcl 8.4.
if {![package vsatisfies [package provide Tcl] 8.4]} {return 0}
if {[catch {package require tcllibc}]} {return 0}
set r [llength [info commands ::struct::tree_critcl]]
}
tcl {
variable selfdir
source [file join $selfdir tree_tcl.tcl]
set r 1
}
default {
return -code error "invalid accelerator/impl. package $key:\
must be one of [join [KnownImplementations] {, }]"
}
}
set accel($key) $r
return $r
}
# ::struct::tree::SwitchTo --
#
# Activates a loaded named implementation.
#
# Arguments:
# key Name of the implementation to activate.
#
# Results:
# None.
proc ::struct::tree::SwitchTo {key} {
variable accel
variable loaded
if {[string equal $key $loaded]} {
# No change, nothing to do.
return
} elseif {![string equal $key ""]} {
# Validate the target implementation of the switch.
if {![info exists accel($key)]} {
return -code error "Unable to activate unknown implementation \"$key\""
} elseif {![info exists accel($key)] || !$accel($key)} {
return -code error "Unable to activate missing implementation \"$key\""
}
}
# Deactivate the previous implementation, if there was any.
if {![string equal $loaded ""]} {
rename ::struct::tree ::struct::tree_$loaded
rename ::struct::tree::prune ::struct::tree::prune_$loaded
}
# Activate the new implementation, if there is any.
if {![string equal $key ""]} {
rename ::struct::tree_$key ::struct::tree
rename ::struct::tree::prune_$key ::struct::tree::prune
}
# Remember the active implementation, for deactivation by future
# switches.
set loaded $key
return
}
# ::struct::tree::Implementations --
#
# Determines which implementations are
# present, i.e. loaded.
#
# Arguments:
# None.
#
# Results:
# A list of implementation keys.
proc ::struct::tree::Implementations {} {
variable accel
set res {}
foreach n [array names accel] {
if {!$accel($n)} continue
lappend res $n
}
return $res
}
# ::struct::tree::KnownImplementations --
#
# Determines which implementations are known
# as possible implementations.
#
# Arguments:
# None.
#
# Results:
# A list of implementation keys. In the order
# of preference, most prefered first.
proc ::struct::tree::KnownImplementations {} {
return {critcl tcl}
}
proc ::struct::tree::Names {} {
return {
critcl {tcllibc based}
tcl {pure Tcl}
}
}
# ### ### ### ######### ######### #########
## Initialization: Data structures.
namespace eval ::struct::tree {
variable selfdir [file dirname [info script]]
variable accel
array set accel {tcl 0 critcl 0}
variable loaded {}
}
# ### ### ### ######### ######### #########
## Initialization: Choose an implementation,
## most prefered first. Loads only one of the
## possible implementations. And activates it.
namespace eval ::struct::tree {
variable e
foreach e [KnownImplementations] {
if {[LoadAccelerator $e]} {
SwitchTo $e
break
}
}
unset e
}
# ### ### ### ######### ######### #########
## Ready
namespace eval ::struct {
# Export the constructor command.
namespace export tree
}
package provide struct::tree 2.1.2
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