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Playfair cipher: Difference between revisions
→{{header|Tcl}}: fix method to build digrams
(→{{header|Tcl}}: fix method to build digrams) |
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Line 2,881:
=={{header|Tcl}}==
{{works with|Tcl|8.6}}
Line 2,890 ⟶ 2,888:
variable grid lookup excluder
constructor {{keyword "PLAYFAIR EXAMPLE"} {exclude "J"}} {
}
# Clean up the keyword source
set keys [my Clean [append keyword "ABCDEFGHIJKLMNOPQRSTUVWXYZ"]]
# Generate the encoding grid
set grid [lrepeat 5 [lrepeat 5 ""]]
set idx -1
for {set i 0} {$i < 5} {incr i} {for {set j 0} {$j < 5} {} {
if {![info exist lookup([set c [lindex $keys [incr idx]]])]} {
lset grid $i $j $c
set lookup($c) [list $i $j]
incr j
}
}}
# Sanity check
if {[array size lookup] != 25} {
error "failed to build encoding table correctly"
}
}
# Worker to apply a consistent cleanup/split rule
method Clean {str} {
}
# These public methods are implemented by a single non-public method
forward encode my Transform 1
forward decode my Transform -1
# The application of the Playfair cypher transform
method Transform {direction message} {
set c0 $c
} else {
lappend digraphs $c0 $c
unset c0
} else {
lappend digraphs $c0 "X"
set c0 $c
}
}
}
if {[info exists c0]} {
# Encode the digraphs
foreach {a b} $digraphs {
lassign $lookup($a) ai aj
lassign $lookup($b) bi bj
if {$ai == $bi} {
set aj [expr {($aj + $direction) % 5}]
set bj [expr {($bj + $direction) % 5}]
} elseif {$aj == $bj} {
set ai [expr {($ai + $direction) % 5}]
set bi [expr {($bi + $direction) % 5}]
} else {
set tmp $aj
set aj $bj
set bj $tmp
}
lappend result [lindex $grid $ai $aj][lindex $grid $bi $bj]
}
# Real use would be: return [join $result ""]
return $result
}
}</lang>
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<pre>
Original: Hide the gold in...the TREESTUMP!!!
Encoded: BM OD ZB XD NA BE KU DM UI XM
Decoded: HI DE TH EG OL DI NT HE TR EX
</pre>
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