package require Itcl
itcl::class BiDirectionalIterator {
variable pos -1
variable end -1
method first {} {
set pos 0
return $this
}
method next {{inc 1}} {
set pos [expr {$pos + $inc}]
if {$pos <= $end} {
return $this
}
return {}
}
method prev {{decr 1}} {
set pos [expr {$pos - $decr}]
if {$pos >= 0} {
return $this
}
return {}
}
method last {} {
set pos $end
return $this
}
method value {} abstract
}
itcl::class String {
inherit BiDirectionalIterator
variable string
constructor {str} {
set string $str
set end [string length $str]
}
method value {} {
return [string index $string $pos]
}
}
itcl::class Tuple {
inherit BiDirectionalIterator
variable tuple
constructor {tp} {
set tuple $tp
set end [llength $tuple]
}
method value {} {
return [lindex $tuple $pos]
}
}
proc reverse {obj} {
set iter [$obj last]
puts -nonewline "Reversed = <"
while {$iter != {}} {
puts -nonewline [$iter value]
set iter [$iter prev]
}
puts ">"
}
proc every_other {obj} {
set iter [$obj first]
puts -nonewline "Every other = <"
while {$iter != {}} {
puts -nonewline [$iter value]
set iter [$iter next 2]
}
puts ">"
}
String s "Hello World!"
Tuple t {1 2 3 4 5 6}
reverse s
reverse t
every_other s
every_other tCategory Itcl Category Data Structure