Help with understanding Pseudo-code

Question

Hi all.

Can someone please tell me how I can implement the following line of pseudo-code.

c[k]=c[k] (mod M) with |c[k]|<=M/2

I do not understand what the 'with' means, does it mean that I have to ensure that after reduction modulo M, c[k] must be less than or equal to M/2. What does 'with' usually mean (if anything) in pseudo-code?

Note that M is of type int. I'm implementing this in Java if it helps.

Thanks in advance.

Answer 1

Is this necessarily pseudo-code? Typically, pseudo-code is just describing what code will do, but in a more natural language (e.g. more like English). In this case, I'm not exactly sure what is even being described. Additionally, I don't think 'with' necessarily has a specialized meaning, especially without seeing the context of the rest of what is written. It might be helpful if you provide more information.

Answer 2

I think it means set c[k] = c[k] + x*M, where -M/2 <= c[k] + x*M <= M/2 (choose the positive or negative integer x such that this is true).

For example, if M = 5, we would have:

       Previous value         New value
          of c[k]              of c[k]
            8                    -2
            9                    -1
           10                     0
           11                     1
           12                     2
           13                    -2

Answer 3

Hmm. Sloppy pseudo-code, heh. But I think he is saying that the absolute value of c[k] will be less than or equal too the modulo value of M divided by 2. This is more or less just a guess however. I have never encountered pseudo code with this terminology (the with) being used. Maybe he is just trying to let people know that c[k] is always insured to be with in bounds because of the modulo arithmetic.

Answer 4

c[k]=c[k] (mod M) with |c[k]|<=M/2

if(Math.abs(c[k]) <= M/2){
  c[k] %= M;
}

The "With" comes from mathematics, and means "If the condition is true, then do so"

You've tagged this "java", so I used the Java math library.