question about the first boolean assignment in Mc Cue,s e-book

[hollow thorn]

I,m doing the e-book modern java from mr. Mc Cue and I don,t understand the boolean
assignment no. 1:

I solved it correctly, but it was a guess.
I noted it written out to understand it.
Did I interpreted it correctly or not?

public void main(){

boolean a = true;
boolean b = false;
boolean c = true;
boolean d = false;

boolean result = a || b && c || !d;
// true || false && true || NOT false = true
// true OR  false AND true = false) OR true
// true OR false OR true = true??


IO.println(result); // true

}

[lusty mural]

<@&987246399047479336> please have a look, thanks.

[drowsy halo]

best to put it into a codeblock to render properly:

void main() {
    boolean a = true;
    boolean b = false;
    boolean c = true;
    boolean d = false;

    boolean result = a || b && c || !d;

    IO.println(result);
}

[hollow thorn]

sorry, I see discord does something weird to my text.

[drowsy halo]

yeah markdown uses || to hide spoiler text

anyways, how would you go about this task
you would go from left to right with proper precedence

so a || b first, what does this evaluate to?

[hollow thorn]

here,s my full code block:

    boolean a = true;
    boolean b = false;
    boolean c = true;
    boolean d = false;

    boolean result = a  b && c  !d;
    // true  false && true  NOT false = true
    // true OR  false AND true = false) OR true
    // true OR false OR true = true??


    IO.println(result); // true
}```

[lusty mural]

Detected code, here are some useful tools:

Formatted code

public void main() {
  boolean a = true;
  boolean b = false;
  boolean c = true;
  boolean d = false;
  boolean result = a b && c!d;
  // true  false && true  NOT false = true
  // true OR  false AND true = false) OR true
  // true OR false OR true = true??
  IO.println(result);
  // true
}

[hollow thorn]

true OR false

[drowsy halo]

that means it results into?

[hollow thorn]

False

[drowsy halo]

its actually true

[hollow thorn]

loool see

[drowsy halo]

a or b is true if at least one of them is true

[hollow thorn]

ooo yes because it,s the OR and not the AND

[drowsy halo]

ok so we have true && c which is?

well I think I am doing it wrong now myself 💀

have to keep in mind operator precedence

so b && c gets executed first 😅

[hollow thorn]

false && true = false

[drowsy halo]

yeah mb that order isnt correct

[hollow thorn]

yes I think I see it now,
a = true OR b && c which is false && true = false
so true OR false
then we have OR !d = NOTfalse = true.

in the end we have:

true OR false OR true

but couldn,t the answer then not also be false?
because it,s OR?

[hollow thorn]

discord is not making it easy with not showing the OR signs

[drowsy halo]

wdym "it could"
true OR false OR true

evaluates from left to right, true || false is true, then we got true || false again which is also true

kinda hard to follow lol

[hollow thorn]

yeah am sorry, but you did make me see why I am confused

I thought true || false could both run because of the OR
But you,re saying it always is true in that case

ooo right, because then the if statement (for example) will run

[wise crow]

a || b && c || !d;
if a is true, it stop and is true
if a is false, it check if b and c are true for the 2,
if b and c are somehow false, it check if d is false

|| can be read as if everything before it is false, try the next

[prime sigil]

no spoonfeeding please. let them find the answer with our help themselves

[lusty mural]

@hollow thorn

Your question has been closed due to inactivity.

If it was not resolved yet, click the button below to keep it
open, or feel free to create a new thread.

Note that usually the reason for nobody calling back is that your
question may have been not well asked and hence no one felt confident
enough answering.

When you reopen the thread, try to use your time to improve the quality
of the question by elaborating, providing details, context, all relevant code
snippets, any errors you are getting, concrete examples and perhaps also some
screenshots. Share your attempt, explain the expected results and compare
them to the current results.

Also try to make the information easily accessible by sharing code
or assignment descriptions directly on Discord, not behind a link or
PDF-file; provide some guidance for long code snippets and ensure
the code is well formatted and has syntax highlighting. Kindly read through
https://stackoverflow.com/help/how-to-ask for more.

With enough info, someone knows the answer for sure 👍

[hollow thorn]

Yes thank you, i figured out my confusion with squidXTV

[hollow thorn]

Yes agreed i managed to solve the second assignment and understand my mistake now.

[lilac torrent]

this is actually one of my favorite challenges in the book since it seems to trip everyone up in a productive way

[hollow thorn]

Hahaha good to know i,m not the only one.

Can I ask: would that 3rd challenge about booleans. The exclusive one, involve if statements? Or can it be solved with less code?

[lilac torrent]

There are many ways to solve it

the point is to force you to find a way to

once you've done that i can show you some short ones

[hollow thorn]

okay, I will share my solution once I tested it! thnx!

[hollow thorn]

   // Change these two variables to test your solution
    boolean hasIceCream = true;
    boolean hasCookie = false;

    boolean validChoice = true;

    if (hasIceCream == true && hasCookie == true) {
        validChoice = false;
    } else if (hasIceCream == false && hasCookie == false) {
        validChoice = false;
    }

    IO.println(validChoice);      
    
}```

[lusty mural]

Detected code, here are some useful tools:

[lilac torrent]

okay so here is another way

public void main(){
   // Change these two variables to test your solution
    boolean hasIceCream = true;
    boolean hasCookie = false;

    boolean validChoice = !(hasIceCream && hasCookie) && (hasIceCream || hasCookie);
}

so "not both, but at least one"

public void main(){
   // Change these two variables to test your solution
    boolean hasIceCream = true;
    boolean hasCookie = false;

    boolean validChoice = !((hasIceCream && hasCookie) || (!hasIceCream && !hasCookie));
}

this is what you wrote, more or less

NOT (both or none)

also works

[hollow thorn]

Would one solution be preferred and why?

Syntax is shorter, so it saves time in readability?

[prime sigil]

shorter doesnt always mean easier to read/understand

[smoky lodge]

for readability, you might just do boolean validChoice = (hasCookie != hasIceCream) to say they can have either/or but not none or both.

[prime sigil]

or u make intermediate bools: hasBoth, hasNone

well named variables help a lot

[smoky lodge]

Also not mentioned in the book,
https://en.wikipedia.org/wiki/De_Morgan's_laws

[hollow thorn]

I would not have come up with this one. It took me a bit to understand. Do you have a few more challenges to practice?

[hollow thorn]

This is complicated!! Pffff
I do not know these mathematical syntax. I,ll look it up and see if it helps or confuses me more 😅

[lilac torrent]

1 sec

https://web.mit.edu/6.111/www/s2007/PSETS/pset1.pdf

https://ocw.mit.edu/courses/6-111-introductory-digital-systems-laboratory-spring-2006/

https://ocw.mit.edu/courses/6-111-introductory-digital-systems-laboratory-spring-2006/resources/l2_combi_logic/

here is a good pdf

[smoky lodge]

Sorry, Wikipedia math is the worst kind of math (assumes PhD level.) Anyway, the demorgan's law is the most recognized transformation for boolean algebra. If you have an AND you can turn it into a OR (or vice versa) and possibly make your statement more readable. Generally, there's little use for these types of boolean statements in the wild since anything over two conditions is a code smell in my book. For more complicated scenarios there's Karnaugh Maps as a tool to reduce boolean conditions, but that usually more in the circuit design realm and when you have conditions that you 'don't care' about.