How to get nil if occur unknown name error。 about expr HOT 5 CLOSED

Can you show me an example?

from expr.

I found an error, what you cannot compare to nil. Will fix it.

from expr.

This is correct because of parameter A.

This is wrong because the C parameter is not found, but I want the result: nil。
I don't want the execution of the terminal program. If I can't find the parameters, I use nil to compare with other parameters and finally get an execution result.

from expr.

Okay, I see. The whole point of expr.Env option is to define everything on compile time. The simplest solution is to omit Env param or pass nil there.
But if you want to partially check variables, but be able to use undefined variables, I think we can use something like expr.AllowUnknownVariables() option.

Also, take a look at this commit: 85ffe57
There is an example with undefined variables.

from expr.

Thank you very much, great！！！

from expr.