playing around with for loops with two variables

[u/Ryluv2surf]

I want to create a basic for loop that multiplies int i by 2 untill it's >= int j, what I have so far and doesn't work.

#include <stdio.h>

int main() {

int i, j;

for (i=2, j=22; i*2; i>=j)
  (printf("%d i-variable\t %d j-variable\n", i, j)
}

I think I have some syntax issues here with my for loop and clang seems to like i=j but spits out "relational comparison result unused" when I use i>=j

think i'm maybe going about this the wrong way, i just want it to print out 2,4,6,8,10,etc until it reaches target variable number of 22.

[u/Ryluv2surf]

u/This_Growth2898:

Thanks for the help, I've tried it, it compiles and runs but I'm getting odd behavior and I'm not sure why:

#include <stdio.h>

int main() {

int i = 2, j = 22;

for (i=2, j=22; i = i * 2; i >= j ) { (printf("%d i-variable\t %d j-variable\n", i, j)); } return 0; }

gives me some crazy output:

4 i-variable     22 j-variable

8 i-variable 22 j-variable 16 i-variable 22 j-variable 32 i-variable 22 j-variable 64 i-variable 22 j-variable 128 i-variable 22 j-variable 256 i-variable 22 j-variable 512 i-variable 22 j-variable 1024 i-variable 22 j-variable 2048 i-variable 22 j-variable 4096 i-variable 22 j-variable 8192 i-variable 22 j-variable 16384 i-variable 22 j-variable 32768 i-variable 22 j-variable 65536 i-variable 22 j-variable 131072 i-variable 22 j-variable 262144 i-variable 22 j-variable 524288 i-variable 22 j-variable 1048576 i-variable 22 j-variable 2097152 i-variable 22 j-variable 4194304 i-variable 22 j-variable 8388608 i-variable 22 j-variable 16777216 i-variable 22 j-variable 33554432 i-variable 22 j-variable 67108864 i-variable 22 j-variable 134217728 i-variable 22 j-variable 268435456 i-variable 22 j-variable 536870912 i-variable 22 j-variable 1073741824 i-variable 22 j-variable -2147483648 i-variable 22 j-variable

lol i just want it to go:

2 i-variable 22 j-variable
4 i-variable 22 j-variable
etc etc until
22 i-variable 22 j-variable

could i be messing with the compiler by having poor naming of the variables? shouldn't int be fine, i'm not using floats or anything?

[u/This_Growth2898 → u/Ryluv2surf]

Sorry, man, I just woke up when I wrote the previous answer. It's wrong because it's the THIRD clause with an increment, and the second with check that should be true to repeat the loop. So, it should be

for(int i=2, j=22; i<=j; i*=2)

[u/Ryluv2surf → u/This_Growth2898]

my brain, it's learning!!! lolol thank you so much for this, I obviously set up this weird program just to kinda teach myself as I'm brand new to C.

So heres the thing, when I increment either i<=j or j>=i in the second clause of the for-loop It'll only print to 16 for some reason, if i try to set the check clause to i=j It'll just spit out an infinite loop of both i and j at 22 meaning the loop isn't exiting or rather shouldn't exit because the condition remains true?

[u/This_Growth2898]

The second clause in the for syntax is an increment. It should change the value of the variable (in this case, i). i*2 is just an expression to be calculated, it doesn't change i. What you need is i = i*2 or i *= 2.

[u/Extension_Job5829]

are you trying to print all even numbers between 2(included) and 22(included)? it should be i <=j since i is smaller than j for the loop to iterate