Interpretation of a given while loop argument

hi all. can anybody tell me what the following while loop gets as an argument? here changeinvoltage_load and changeinvoltage_pv are the two vectors. and iter is the counter of the loop. initially it is zero.

iter=0;
  while any(~(abs(changeinvoltage_load)<=0.00001)) && any(~(abs(changeinvoltage_pv)<=0.00001)) &&   iter > 1 && iter <100   ;
      iter=iter+1;
      do the following.......

    end

Answer 1

[Walter Roberson]

That while will be asked to process the result of

any(~(abs(changeinvoltage_load)<=0.00001)) && any(~(abs(changeinvoltage_pv)<=0.00001)) &&   iter > 1 && iter <100

That is a series of conditions separated with && . In order to use && each of the conditions must evaluate to a scalar.

any(~(abs(changeinvoltage_load)<=0.00001))

will evaluate to a scalar provided that ~(abs(changeinvoltage_load)<=0.00001) evaluates to a scalar or to a vector. The code would have a problem if changeinvoltage_load were a 2D array. With a vector, each of the individual logical values (abs(changeinvoltage_load)<=0.00001) would be calculated, each of them would be logically negated because of the ~, and then any() would return true if at least one of those values were true. An equivalent expression would be

any( abs(changeinvoltage_load) > 0.00001 )

The second sub-expression any(~(abs(changeinvoltage_pv)<=0.00001)) follows the same logic.

The third subexpression iter > 1 is scalar true provided that iter is larger than 1. If iter is less than or equal to 1 at the start then the condition would be false and that would make the overall && false, leading to the while loop body never being executed. You initialize iter = 0, so the body of the while loop is never executed.

The fourth subexpression iter < 100 is scalar true provided that iter is less than 100. If iter is 0 or 1 at the beginning then the condition would not be reached because the previous condition would have been false.

There is probably no good reason for having the iter > 1 test in the while unless you want to be able to disable the while loop.