What does "|=" mean in pseudocode?

Question

I'm trying to implement the following pseudocode:

But I fail to understand what the line

state_val |= (c(s) == True) << i++

does. To give some context, this pseudocode is found in this paper from MIT, and c(s) is an operation that returns True or False based on s.

Does this answer your question? [What does "|=" mean? (pipe equal operator)](https://stackoverflow.com/questions/14295469/what-does-mean-pipe-equal-operator) — Reine_Ran_, Mar 28 '20 at 14:59

score 3 · Accepted Answer · answered Mar 28 '20 at 14:55

a |= b means that a will be set to the bitwise OR of a and b. Essentially, state_val is a number whose bits represent booleans, and its binary representation will look something like this:

c7(s) c6(s) c5(s) c4(s) c3(s) c2(s) c1(s) c0(s)

Where c0 is the first c, c1 is the second, etc. If c7(s), c5(s), and c1(s) were true, then state_val would be 10100010 in binary or 162.

score 1 · Answer 2 · answered Mar 28 '20 at 14:54

1

It's bitwise OR. Basically shorthand for

state_val = state_val | ((c(s) == True) << i++)

answered Mar 28 '20 at 14:54

bottaio

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Thanks, and what does the `((c(s) == True) << i++` part do exactly – Thomas Wagenaar Mar 28 '20 at 14:57
i++ -> increment; c(s) == True -> check if score is true; value << number - bitshift number times – bottaio Mar 28 '20 at 14:58
and why is it not in a seperate line? i'm not sure what the `<<` is doing – Thomas Wagenaar Mar 28 '20 at 14:59
1

@ThomasW Left shift. If `c(s)` is true, then it's `1 << i++`, otherwise `0`. It's like `1 * 2**i++` (two to the power of `i`, increment `i`) – S.S. Anne Mar 28 '20 at 14:59
it's quite common syntax, once you are familiar with that it's easier to read – bottaio Mar 28 '20 at 14:59

What does "|=" mean in pseudocode?

2 Answers2