GNU Octave

Time for action – working with precedence rules

1. Let us see an example:

   octave:117> A*y + a
   
   ans =
       2.5000
      -3.0000
       1.7500
   

   Here, Octave first performs the matrix multiplication between A and y, and then adds a to that result. We say that multiplication has higher precedence than addition.

2. Let us try two other examples:

   octave:118> A*y.^2
   
   ans =
     4.2500
   -18.5000
     2.3750
   
   octave:119> (A*y).^2
   
   ans =
        0.2500
       25.0000
        0.0625
   

What just happened?

In command 118, because the .^ operator has higher precedence than *, Octave first calculates element-wise power operation y.^2, and then performs the matrix multiplication. In command 190, by applying parenthesis, we can perform the matrix multiplication first, and then do the power operation on the resulting ...