Is there nothing wrong with digits in identifier name?

问题

Since in C\C++\Java -

int 2a ; //invalid suffix "a" on integer constant

Is there nothing wrong with digits in the rest of variant name although it's valid syntax ?

Like -

int num1 ;
int num_1st ;
int num_2nd ; 

回答1:

I've never heard of anybody (e.g., any coding standards/guidelines) that had a problem with digits in an identifier. Nonetheless, too many of them can indicate that a vector or array might be preferable -- even with only two, your num_1st and num_2nd might be better as numbers[2].

回答2:

An identifier cannot start with a number. It must start with a letter or an underscore.

回答3:

Variables identifier must start with a letter or an underscore, but the rest of the characters can be letter, underscore or a digit.

You can even decalre a variable: int _ = 0;

Or if you are familiar with regular expression, it can be patterned as: "[a-zA-Z_]\w*?\b"

Where the \w*? part is not a must.

回答4:

Answer is, no there is nothing wrong with numbers in the rest of the identifier name.

回答5:

As long as variable names are meaningful, using digits as part of the name is definitely not a bad thing. Of course, having a large number of similarly named variables with just a number at the end to differentiate them could be a sign of bad design.

The reason for nor allowing identifiers starting with digits, I'm pretty sure, is that it makes it so much easier to write the parser:

c = getchar(); 
ungetc(c);
if (isdigit(c)) 
   token = number(); 
else 
   token = identifier(); 

回答6:

This is the rule off identifier that it must start with an letter or an underscore after that only digits are allowed.

来源：https://stackoverflow.com/questions/13977739/is-there-nothing-wrong-with-digits-in-identifier-name