Q: Is there a maximum length or other restrictions on variable names in the LP file?

[hvoerman]

Is there a maximum length or other restrictions on variable names in the LP file?

[chriswasser]

I've ran into a similar question after receiving errors on my chosen names so I looked at the source code myself and found the following points of reference:

• the is_invalid_name implementation in CoinUtils
• the notes section in the associated header
• the documentation for is_invalid_name

At this point in time, the restrictions on variable (, constraint, and objective function) names in LP files seem to be:

• the name length must be <= 100 characters (or <= 96 characters for ranged constraints since _low is appended to the name of the lower bound constraint)
• the name can only contain any of these characters: 1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\"!#$%&(),.;?@_'{}~ and the backtick character which does not play nicely in this markdown
• the name cannot be empty
• the name cannot start with a number i.e. not with any of these characters: 1234567890
• the name cannot be a keyword as defined here i.e. not any of these names with any capitalization: bound, bounds, integer, integers, general, generals, binary, binaries, semi-continuous, semi, semis, sos, end
• the name cannot be any other reserved keyword as defined here i.e. not any of these names with any capitalization: free, inf

Hope this helps 🤓

Greetings

[hvoerman]

Hopefully the above can be confirmed by one of the CBC developers.

@chriswasser: thanks very much for this investigation!