Looking for critique. Teaching myself C.

jmgibson1981 · 01-08-2023, 10:21 PM

Indeed. I made that change. I spent the day doing a few other calculators as well. Also learned to how to include another .c file so I've got a mylibs.c started which 3 of my little programs currently include. Just one function at the moment. I've managed to build these other ones with zero output from

Code:

gcc -Wall -O1 -o $file $file.c

That one eludes me though, the original calc.c. It just tosses a single issue that I just cannot sort out. It works, more of a notification from that gcc command than anything I guess. Worked on that one quite a bit today trying to isolate it.

ntubski · 01-09-2023, 08:29 AM

Quote:

Originally Posted by jmgibson1981

Indeed. I made that change. I spent the day doing a few other calculators as well. Also learned to how to include another .c file so I've got a mylibs.c

FYI, it's usually a bad idea to include .c files. Typically only .h files are included. For multiple .c files, you would usually compile each of them to .o files which are then linked together. This means that if you change only one .c file, you don't have to recompile the others. You can use a Makefile to manage that.

Quote:

That one eludes me though, the original calc.c. It just tosses a single issue that I just cannot sort out. It works, more of a notification from that gcc command than anything I guess. Worked on that one quite a bit today trying to isolate it.

Ah, I guess gcc doesn't do the inference you expect there. Anyway, I think the best way is to add a default: case into the switch statement, since again with a separate if you end up with two lists of legal operators (and also, gcc won't be confused about it).

jmgibson1981 · 01-10-2023, 04:41 PM

I found it. i'm not sure it's what you suggested, may be. I found somewhere that setting a variable inside braces keeps it in those braces, at least as far as the compiler output. It worked but it wasn't perfect. I've since simplified my calcs down to a single one that does float. I made a solution_check function and just call it after setting the solution in each operation instead of once for the entire function. Not a peep from

Code:

gcc -Wall -O1 -o $file $file.c

ntubski · 01-10-2023, 05:16 PM

Hmm, calling exit(0) like that looks kind of odd to me. What I had in mind was more like

Code:

switch (op) {
case '+': ...
case '-': ...
case '*': ...
case '/': ...

default:
   printf("invalid operator %c\n", op);
   exit(1);
}

print_the_answer(...);

jmgibson1981 · 01-10-2023, 06:00 PM

Indeed. that would be better. thank you much

pan64 · 01-11-2023, 03:46 AM

Quote:

Originally Posted by ntubski

Hmm, calling exit(0) like that looks kind of odd to me. What I had in mind was more like

Code:

switch (op) {
case '+': ...
case '-': ...
case '*': ...
case '/': ...

default:
   printf("invalid operator %c\n", op);
   exit(1);
}

print_the_answer(...);

you are right, theoretically we need only return something at the end of the main, calling exit in the middle is not really nice.

To OP:
if you have more than one .c files you can write a small makefile to build your executable, in that case you only need to run make (to make it).
https://www.gnu.org/software/make/ma...imple-Makefile

sundialsvcs · 01-11-2023, 03:19 PM

I can accept this use of "exit(1)" because this is an exception. The program cannot complete and produce an answer. Therefore it exits, returning a "nonzero return code" as a well-understood indication that "something went wrong."

pan64 · 01-11-2023, 03:22 PM

Quote:

Originally Posted by sundialsvcs

I can accept this use of "exit(1)" because this is an exception. The program cannot complete and produce an answer. Therefore it exits, returning a "nonzero return code" as a well-understood indication that "something went wrong."

in this case yes, in a real program you need to do some cleanup (for example). But that is another topic.

ntubski · 01-11-2023, 04:56 PM

Quote:

Originally Posted by sundialsvcs

I can accept this use of "exit(1)" because this is an exception.

Yes, I was talking about exit(0) as seen in https://gitlab.com/jmgibson1981/mycp...r/calculator.c

Code:

		case '+': // addition working
			solution = num1 + num2;
			solution_check(solution);
		case '-': // subtraction working
			solution = num1 - num2;
			solution_check(solution);
[...]

// verify solution exists and exit 0. 1 if fail

void solution_check(float solution) {
	if (solution) {
		printf("answer is %.3f\n", solution);
		exit(0);
	} else {
		printf("unable to complete calculation\n");
		exit(1);
	}
}

NevemTeve · 01-11-2023, 05:35 PM

So `5 - 5` would be problematic?

sundialsvcs · 01-11-2023, 06:24 PM

Quote:

Originally Posted by pan64

... But that is another topic.

Yes. We need to be sure that we don't scare him off.