A v-string, such as v65.66.67, is encoded as a character string with no special type designation. So, when given a parameter that might be a v-string or might be something else, how do you tell them apart?

I think I came up with an efficient and useful way:

I'll treat it as a v-string if it contains any characters in the range \0-\1F. Most v-strings will contain entirely values in that range anyway, and real words (including specifically version designators spelled out as ascii numbers and identifiers) will not contain non-graphic control codes. Maybe I'll leave out \t and \n and \r just to be safe.

Two key points to this: I can perform the check using the fast counting mode of tr; and more importantly a v-string that is not usual, like the one in the first sentence, can be distinguished by adding a trailing .0 which does not affect the meaning.

What do y'all think? Any better ideas?

—John

In reply to Distinguishing a v-string from something else by John M. Dlugosz

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