Order of operations - what is 6÷2(1+2) ?

[Albert Chan]

(12-22-2020 08:03 PM)robve Wrote:  Yes for Prolog:
?- X is -2^2.
X = 4.

Prolog should return -4 for this, according to its precedence table. (pow higher than unary minus)

Problem is it parsed first number as -2, removed the unary minus.
Forcing it to parse first number as 2, we get the right answer.

B-Prolog Version 8.1, All rights reserved, (C) Afany Software 1994-2014.
| ?- X is -2**2
X = 4
yes
| ?- Two = 2, X is -Two**Two
Two = 2
X = -4
yes

You should not get 2 different answers by replacing Two for 2.
This bug had been fixed in Picat

Picat> X is -2**2
X = -4
yes
Picat> Two = 2, X is -Two**Two
Two = 2
X = -4
yes