Re: Arithmetic pow results incorrect in arithmetic expansion.

[Chet Ramey]

On 1/8/21 11:19 PM, Hyunho Cho wrote:

> Bash Version: 5.0
> Patch Level: 17
> Release Status: release
>
> ####################################################################
>
> i have tested below in gnome calculator, Qalculate, gawk, perl
> and all results in -4 but bash is 4
>
> $ awk 'BEGIN { print -2 ^ 2 }'
> -4
>
> $ perl -E 'say -2 ** 2'
> -4
>
> $ echo $(( -2 ** 2 ))                     # only bash results in 4
> 4

This is how bash does operator precedence.

Like C, unary plus and minus are operators that have higher precedence
than any of the mathematic operators (multiplication/division/addition/
subtraction/etc). So unary operators have a higher precedence than
exponentiation.

This behavior varies widely among programs that implement exponentiation
operators.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/