variable symbols 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
proc add_baseX {numA numB} {
# add two numbers in any base that can be expressed as a string of
# unique symbols
#
# John Ellson <ellson@lucent.com>
variable symbols
set base [string length $symbols]
set idxA [string length $numA]
set idxB [string length $numB]
set carry 0
set result ""
while {$idxA || $idxB || $carry} {
if {$idxA} {
set digA [string index $numA [incr idxA -1]]
set decA [string first $digA $symbols]
if {$decA < 0} {
puts stderr "invalid digit \"$digA\""
return -1
}
} else {
set decA 0
}
if {$idxB} {
set digB [string index $numB [incr idxB -1]]
set decB [string first $digB $symbols]
if {$decB < 0} {
puts stderr "invalid digit \"$digB\""
return -1
}
} else {
set decB 0
}
set sumdec [expr {$decA + $decB + $carry}]
if {$sumdec >= $base} {
set carry 1
incr sumdec -$base
} else {
set carry 0
}
set result [string index $symbols $sumdec]$result
}
return $result
}
