Interesting last two:

Evaluate ( "2 + 1" ) = 3

Evaluate ( "- 2 + 1" ) = -1

Evaluate ( "+ + + 2 + + + 1" ) = 3

Evaluate ( "+ + + 2 + - + 1" ) = 1

It makes sense: minus inverts, plus doesn't. "2 + - + 1" could be rewritten as:

2 + 1 * (-1) * 1

Yes, I undersood the minus but I was surprised that the Evaluate ( ) worked with more signs.

( while Evaluate ( "2+1+" ) I know that doesn't work )

The surprise was coming while I made a substitution of ¶ with + in a List where there was some "¶¶"

It may seem a bit unnatural - but it's not much different from "not not 1".

NOW it makes sense :

P.S: This is nice, too:

Abs ( + + + 1 + + + - + 3 )

( w/o any quote )

So, for the calculation engine, this is a number:

+ + + 1 + + + - + 3

I am not sure it's a number, but it evaluates to a number.