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got him (lemy.lol)

submitted 6 months ago by ngn@lemy.lol to c/programmerhumor@lemmy.ml

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[–] fluckx@lemmy.world 11 points 6 months ago* (last edited 6 months ago) (2 children)

p = 1

x = ++p
// x = 2
// p = 2

p = 1
x  = p++
// x = 1
// p = 2

++p will increase the value and return the new value

p++ will increase the value and return the old value

I think p = p + 1 is the same as p++ and not as ++p. No?

[–] Tyoda@lemm.ee 10 points 6 months ago* (last edited 6 months ago) (1 children)

In C an assignment is an expression where the value is the new value of what was being assigned to.

In a = b = 1, both a and b will be 1.

a = *(p = p + 1)

is the same as

p += 1
a = *p

, so ++p.

[–] fluckx@lemmy.world 1 points 6 months ago

What I meant was:

In the screenshot it said x = *(++p) and iirc that is not the same as saying x = *(p++) or x = *(p += 1)

As in my example using ++p will return the new value after increment and p++ or p+=1 will return the value before the increment happens, and then increment the variable.

Or at least that is how I remember it working based on other languages.

I'm not sure what the * does, but I'm assuming it might be a pointer reference? I've never really learned how to code in c or c++ specifically. Though in other languages ( like PHP which is based on C ) there is a distinct difference between ++p and (p++ or p+= 1)

The last two behave the same. Though it has been years since I did a lot of coding. Which is why I asked.

I'll install the latest PHP runtime tonight and give it a try xD

[–] SpaceNoodle@lemmy.world 3 points 6 months ago* (last edited 6 months ago) (1 children)

(p += 1) resolves to the value of p after the incrementation, as does ( p = p + 1).

[–] fluckx@lemmy.world 2 points 6 months ago (1 children)

Yes.

p++ == p+= 1 == p = p + 1 are all the same if you use it in an assignment.

++p is different if you use it in an assignment. If it's in its own line it won't make much difference.

That's the point I was trying to make.

[–] SpaceNoodle@lemmy.world 5 points 6 months ago (1 children)

No.

++p returns incremented p.

p += 1 returns incremented p.

p = p + 1 returns incremented p.

p++ returns p before it is incremented.

[–] fluckx@lemmy.world 3 points 6 months ago

Right. So i had them the other way around. :D

Thanks for clarifying.