Question

i am trying to validate a custom expression. This expression contains the follow conditions:

• Number position;
• Type operation;
• Expression;
• Alias (optional);
• Comment (optional);

The conditions are separated by “|” pipe. So, four pipes is the limit.

So, to be a valid expression:

0|S|write(&var1)|alias1|my coment – OK
0|K|write(&var1)|alias1|my coment – FAIL
1|I|read(&var2)|alias2| – OK
1|S|read(&var1)|| – OK
2|N|if(&var1 == &var2);read(&var3)|| – OK
3|S||| – FAIL
3|I|write(&var1)|alias 3| – FAIL
3|N|write(&var1)|alias1|my coment| – FAIL

I am using this ER to validate:

^(\d{1,10})\|(S|M|I|N)\|(.+?)\|([a-zA-Z0-9]+)?\|(.+)?

But i can not validate the expression that ends with pipe. Because, in a comment can have any caracter except a pipe…

Some idea??

Thanks

Answer 1

Try using [^|] instead of (.+)? at the end of your regex:

^(\d{1,10})\|(S|M|I|N)\|[^|]+\|([a-zA-Z0-9]*)\|([^|]*)$

As a side note: for every sub-expression subexpr the following regexes are equivalent:

((subexpr)+)?

and

(subexpr)*