Re^2: Questions: how to exclude substring having Evil meanings

There are limitations and drawbacks.

It's hard to name most characters. "I have a problem with invoice latin-small-letter-a-with-dot-above-and-macron;devanagari-letter-vocalic-r;left-right-white-arrow." (ǡऋ⬄)
There are font problems ("I have a problem with invoice box-box-box.")
Encoding problems are still common too.

What symbols are you suggesting?

You'd need a set of 22 chars to maintain a record num of 5 chars. (22⁵ = 5,153,632).
You'd need a set of 48 chars to bring the record num down to 4 chars. (48⁴ = 5,308,416).
You'd need a set of 171 chars to bring the record num down to 3 chars. (171³ = 5,000,211).

I suppose you could use the horizontal dominoes. Each domino can be read as two digits from 0 to 6. For example, this is node 🀷🁜🁑🀵 (06:61:44:04₇).

Using dominoes would reduce the record num to 4 chars (7^2⁴ = 5,764,801) assuming you didn't want the sequence to be a legal domino sequence. Both the UTF-8 and the UTF-16 encoding of 4 dominoes would take 16 bytes. (UTF-32 too, for what it's worth.)

Update: Added everything after the question.

Comment on Re^2: Questions: how to exclude substring having Evil meanings

Replies are listed 'Best First'.
Re^3: Questions: how to exclude substring having Evil meanings by holli (Abbot) on Dec 03, 2009 at 08:01 UTC
[...] assuming you didn't want the sequence to be a legal domino sequence. What if it had to be legal sequences? holli You can lead your users to water, but alas, you cannot drown them.	[reply] [d/l]
Re^4: Questions: how to exclude substring having Evil meanings by ikegami (Patriarch) on Dec 03, 2009 at 18:46 UTC
Then each domino except the first only counts for one base 7 digit. 16614404₇ would go from 16:61:44:04 to 16:66:61:14:44:40:04. That means that 6 or more decimal digits would then be more efficient than the same amount of dominos. `10^n >= 7^(n+1) ln(10^n) >= ln(7^(n+1)) nln(10) >= (n+1)ln(7) nln(10) >= nln(7) + ln(7) nln(10) - nln(7) >= ln(7) n( ln(10) - ln(7) ) >= ln(7) n >= ln(7)/( ln(10) - ln(7) ) n >= 5.455696235812878344 n >= 6` [download] $ perl -e' printf "chars: %2d digits: %13.f %s dominoes: %11.f\n", $_, 10$_, qw( < = > )[( 10$_ <=> 7($_+1) )+1], 7*($_+1), for 1..12 ' chars: 1 digits: 10 < dominoes: 49 chars: 2 digits: 100 < dominoes: 343 chars: 3 digits: 1000 < dominoes: 2401 chars: 4 digits: 10000 < dominoes: 16807 chars: 5 digits: 100000 < dominoes: 117649 chars: 6 digits: 1000000 > dominoes: 823543 chars: 7 digits: 10000000 > dominoes: 5764801 chars: 8 digits: 100000000 > dominoes: 40353607 chars: 9 digits: 1000000000 > dominoes: 282475249 chars: 10 digits: 10000000000 > dominoes: 1977326743 chars: 11 digits: 100000000000 > dominoes: 13841287201 chars: 12 digits: 1000000000000 > dominoes: 96889010407 [download]	[reply] [d/l] [select]
Re^3: Questions: how to exclude substring having Evil meanings by xyzzy (Pilgrim) on Dec 03, 2009 at 20:38 UTC
I suppose you could use the horizontal dominoes. Each domino can be read as two digits from 0 to 6. This is brilliant. `$,=qq.\n.;print q.\/\/____\/.,q./\ \ / / \\.,q. /_/__.,q..`	[reply] [d/l]