sqrt function in c in a linux environment with gcc as the compiler

[Souranil21 chakraborty]

hey anyone help me with a function in c? i was trying to use the sqrt function to determine the squareroot of an positive interger number through a c program so i included the <math.h> header file and also i am on a linux environment with gcc compiler. So is there any other way to determine the squareroot of a number in a linux environment

 

[AbydosOne]

5 minutes ago, Souranil21 chakraborty said:

hey anyone help me with a function in c?

What are you getting instead of the right answer? Error message?

[Sauron]

there are dozens of alternative math libraries for C but... what's wrong with math.h? Did you forget to link it using the

-lm

gcc parameter?

[wanderingfool2]

2 hours ago, Souranil21 chakraborty said:

hey anyone help me with a function in c? i was trying to use the sqrt function to determine the squareroot of an positive interger number through a c program so i included the <math.h> header file and also i am on a linux environment with gcc compiler. So is there any other way to determine the squareroot of a number in a linux environment

 

The answer can really depend on what you are trying to do, and why you are wanting to use something other than the sqrt function.

 

Could be wrong, but from what I though sqrt in effect gets hardware accelerated (like using the SSE/SSE2 assembly commands for sqrt)...so the processor handles square roots itself (which should make it a lot quicker than code written by hand).

 

I mean, if lets say sqrt isn't doing things the way you want it to (lets say you are trying to processes a weird data type), then you could always just write the sqrt function yourself.  [There are decent examples of C code sqrt functions, even a "fast" but less accurate sqrt function].  I mean Newton's method is fairly simple to implement and decently fast.

 

https://scriptverse.academy/tutorials/c-program-newton-raphson.html

^- Newton's method in C.  No libraries needed at all [Note they hardcoded it to find the value of sqrt(5), but that is easily fixed]

[Souranil21 chakraborty]

11 hours ago, Sauron said:

there are dozens of alternative math libraries for C but... what's wrong with math.h? Did you forget to link it using the

-lm

gcc parameter?

no i  linked it through #include but when i ran the programm after compilation the sytem is throwing an error saying that the sqrt function is not recognized

 

[Souranil21 chakraborty]

12 hours ago, AbydosOne said:

What are you getting instead of the right answer? Error message?

yeah the sqrt function is not recorgnized or something like that the rest of the programme is fine

 

[Souranil21 chakraborty]

5 minutes ago, Souranil21 chakraborty said:

yeah the sqrt function is not recorgnized or something like that the rest of the programme is fine

 

see here i made a quick compilation od just simple c code and see what is the error coming

[AbydosOne]

1 hour ago, Souranil21 chakraborty said:

see here i made a quick compilation od just simple c code and see what is the error coming

Shouldn't it be "Math.sqrt()" and not just "sqrt()"? (I might be thinking of C++ though.)

[wanderingfool2]

2 hours ago, Souranil21 chakraborty said:

see here i made a quick compilation od just simple c code and see what is the error coming

Well you should follow what @Sauron said.  You missed the -lm flag in gcc which means you aren't importing the math library.

 

A note as well, when you have issues such as that it's also really handy just googling the error code.

e.g. The top search result for "undefined reference to sqrt c" returns me to stackoverflow saying to add -lm to the gcc flag. (gcc file1.c -lm)

 

Also, you should be casting the sqrt to an int (sqrt returns a double value)

 

e.g.

#include <stdio.h>
#include <math.h>

int main() {
	int a=4, result;
	result = (int) sqrt(a);
	printf("%d", result);
	return 0;
}

Try something like that, likely will

[Sauron]

3 hours ago, Souranil21 chakraborty said:

no i  linked it through #include but when i ran the programm after compilation the sytem is throwing an error saying that the sqrt function is not recognized

 

You need to link it at compilation time too or it won't be linked

[Nayr438]

8 hours ago, Souranil21 chakraborty said:

see here i made a quick compilation od just simple c code and see what is the error coming

 

You need to link the project against libm at compile time.

 

gcc file1.c -lm -o app_name

 

I would personally recommend learning to use a build system like CMake or Meson, so you can define your project properties once rather than manually at compile time.

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