Plus42 algebraic expressions update

[Vincent Weber]

Thanks Thomas.

Re ITEM, yes, one big let-down on the 27S is that L(ITEM(THING:I):J) triggers a syntax error, while it really shouldn't. This would enable true indirect indexing within the equation language, making it Turing compatible.

Also, it would be great to define functions rather than just equations, like DEF F(X,Y,Z)=X+Y+Z, and reuse them in either equations or RPN program. Now we are talking true programming

Cheers