Invert sign of a numeric variable

[EmanueleBonin]

If i use this syntax : let v=1 let v=-v

Compiler return an error like this: failure at line 1, col 5, after " v=1\nlet v" expected "anything but \"=\""

the workaround is : let v=1 let v=0-v

exists a more elegant way or is this the right way ?

[neilsf]

The unary - operator was dropped somewhere in version 0.9 and has not been re-implemented since. Hopefully I can add it again in version 3.

[neilsf]

Duplicate of #40