In some other answers, this could save well over 2 bytes. (Edit: Indeed, in Is this a Permutation of 1..n it has saved 5 bytes, bringing it down from e.g. 34 bytes to 29 bytes.)
In some other answers, this could save well over 2 bytes.
In some other answers, this could save well over 2 bytes. (Edit: Indeed, in Is this a Permutation of 1..n it has saved 5 bytes, bringing it down from e.g. 34 bytes to 29 bytes.)
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What is a good ASCII boundary-character for regex unary, and will using that instead of a delimiter affect the perceived legitimacy of my answers?
So far, I have only used comma-delimited unary for my answers taking a list / array as input, since it's the "obvious" choice. That looks like xx,xxxxxx,x,xx,x,xxx.
However, this can't differentiate between \$[]\$ and \$[0]\$, as both would be an empty string. In most challenges, this isn't a direct problem since an empty list is allowed to be undefined behavior.
But more to the point, in many answers, it requires using \b where a single byte could have been used instead. I have considered using an input specification where a single character is used not just as a delimiter, but also as a sandwich character for the entire list. So for example using ! would result in input looking like !xx!xxxxxx!x!xx!x!xxx!.
What would be the best name for this type of character (as opposed to "delimiter")?
- framing character
- boundary character
- container character
- something else?
As an example, my recent answer to Visible Dice Faces currently uses , as a delimiter and has a 29 byte shortest solution:
^(?!.*\b(x(\2?+,.*\b)?){7}\b) But using a boundary character, this could be 27 bytes:
^(?!.*:(x(\2?+:.*\b)?){7}:) In some other answers, this could save well over 2 bytes.
So should I go ahead and do this? What about answers where switching from a delimiter to a boundary-character wouldn't result in better golf – should I do it anyway for consistency? (That'd mean lots of old answers to edit, so it might be a bad idea.) What if there's a challenge where it'd actually result in worse golf (seems unlikely, but for sake of argument)?
Would it negatively affect the perceived legitimacy of my answer if I use a boundary-character to improve the golf? As a really extreme example of manipulating the input specification for golf, see my 163 byte answer in Is it a valid chess move? (Python, with python-chess).
And what would be the best choice of ASCII character for this? It has to be a non-word character, because even with a sandwich character, \b still has to be used in some places. What I'm mainly concerned about how readable it is in a regex pattern, and the aesthetics of the choice.
In rough order of my preference:
:-^(?!.*:(x(\2?+:.*\b)?){7}:)- symmetric on two axes; stands out fairly well; is thin horizontally, making it look good as a separator!-^(?!.*!(x(\2?+!.*\b)?){7}!)- symmetric on one axes, but doesn't have much of a connotation of use as a separator; also used in(?!), which might slightly impact readability'-^(?!.*'(x(\2?+'.*\b)?){7}')- symmetric on one axis, but has a weak connotation of strings; doesn't stand out too well in a regex"-^(?!.*"(x(\2?+".*\b)?){7}")- symmetric on one axis, but has a heavy connotation of strings--^(?!.*-(x(\2?+-.*\b)?){7}-)- symmetric on two axes; has a meaning inside regex character classes, but that shouldn't be a problem; doesn't look much like a separator though~-^(?!.*~(x(\2?+~.*\b)?){7}~)=-^(?!.*=(x(\2?+=.*\b)?){7}=)- its mathematical meaning would probably distract too much from using it for this purpose/-^(?!.*/(x(\2?+/.*\b)?){7}/)- commonly used as the delimiter in substitution expressions, so might not be good to apply to this usage as well^(?!.* (x(\2?+ .*\b)?){7} )- not too readable, since it's just a blank space; would make it harder to pretty-print the regex, as the spaces would have to be\-escaped in that version- newline - would require using the
s(DOTALL) flag, and showing the character as\nor¶in pretty-printed listings, and would make the actual regex take up multiple lines. Also already has connotations as a terminator or separator, not a prefix. - tab - same drawbacks as space, but additionally would be hard to distinguish from space, and already has connotations as a separator, not a boundary character.
- NUL - technically difficult to use, but nevertheless usable. However, already has connotations as a terminator, not a prefix.
#-^(?!.*#(x(\2?+#.*\b)?){7}#)- stands out pretty well, but feels too heavy/large to be a separator`-^(?!.*`(x(\2?+`.*\b)?){7}`)- stands out as a particularly small character, but for that same reason, might be harder to read;-^(?!.*;(x(\2?+;.*\b)?){7};)- asymmetric; often used as a line terminator, but would be weird as prefix,-^(?!.*,(x(\2?+,.*\b)?){7},)- asymmetric; already used as a separator, so probably shouldn't be used as a prefix (and would look weird used that way)%-^(?!.*%(x(\2?+%.*\b)?){7}%)&-^(?!.*&(x(\2?+&.*\b)?){7}&)