In csh, why does 4 - 3 + 1 == 0?

Question

#!/bin/csh

@ cows = 4 - 3 + 1
echo $cows

This simple csh script when run produces \"0\" for output when I\'d expect \"2\".

~root:          


        

Answer 1

Operator grouping. It's reading the operation as 4 - (3 + 1), as opposed to (4 - 3) + 1.

Answer 2

The + and - operators are right-associative in csh. This means that '4 - 3 + 1' is evaluated as '4 - (3 + 1)'.

Answer 3

While you are expecting the operators to be left associative, they are right associative in csh, so it's evaluated as 4-(3+1)

   -
  / \
 /   \
4     +
     / \
    3   1