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As I'm sure tons of people are about to point out

if not t.whatever then

is part of the language.  The not operator is cleverly called 'not' already.


>Maybe there is a trick here I don't see, but.....
>Many times in my Lua code, I'll test that a key appears in a table and do
>     if t.whatever then
>         do_something()
>     end
>But today was the first time that I found I needed to test for the opposite
>case-- that of t.whatever not existing.  It's then I realized that Lua
>doesn't have a logical "not".
>It's easy enough to create a function that implements a logical "not":
>     function not(x)
>         if x then
>             return nil
>         else
>             return 1
>         end
>     end
>And use it like this:
>     if not(t.whatever) then
>         do_something()
>     end
>But is forcing a functional syntax and having the cost of of a function
>call what the designers of Lua intended?  I admire the minimalism in Lua,
>but this seems like a pretty basic need for most any language.  Without it,
>you're either forcing the programmer to come up with their own logical
>"not" or forcing them to have an empty "then" clause in an "if," doing the
>work in the "else" clause.