The **`erfl` function** is defined in the `<tgmath.h>` header file in C. It takes in a single parameter: a `long double` value. It then computes the error function of the given argument and returns a value of type `long double`. 

The #key# error function: also known as Gauss error function  #key# in mathematics is defined as follows:

> erf $z$ = $\frac{2}{\sqrt{\pi}}$ $\int_{0}^{arg} e^{-t^2} dt$ 

> The argument to the `erfl` function serves as the upper limit in the integral above.

The error function is often used in probability and statistics. It integrates the normal distribution and gives the probability that a normally distributed random variable Y (with mean 0 and variance ½) falls into the range [−x, x].

The illustration below shows how the `erfl` function works: 

# Declaration

The `erfl` function is defined as follows:

```C
long double erfl(long double arg);
```
It takes in a single value of type `long double` and computes its error function. It then returns the answer of type `long double`.

# Error handling

The `erfl` function returns special values for certain arguments:

* If the argument is +-0, +-0 is returned
* If the argument is +-$\infty$, +- $\infty$ is returned
* If the argument is `NAN`, `NAN` is returned

# Examples

The following code snippet shows how we can use the `erfl` function:

#include <stdio.h> // Including header file for printf function
#include <math.h>  // Including header file for erf function

int main (){

  long double param, result;
  param = 2.0;
  result = erfl(param);
  printf("erfl (%Lf) = %Lf\n", param, result);
  return 0;
}

The following code snippet shows how error handling in the `erfl` function works:

#include <stdio.h> // Including header file for printf function
#include <math.h>  // Including header file for erf function

int main (){
  long double param = 0.0;
  printf("erfl (%Lf) = %Lf\n", param, erfl(0.0));
  return 0;
}

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What is erfl in C?

The erfl function is defined in the  header file in C. It takes in a single parameter: a long double value. It then computes the error function of the given argument and returns a value of type long double. The error functionalso known as Gauss error function in mathematics is defined as follows:  erf zzz = 2π\frac{2}{\sqrt{\pi}}π​2​ ∫0arge−t2dt\int_{0}^{arg} e^{-t^2} dt∫0arg​e−t2dt   The argument to the erfl function serves as the upper limit in the integral above.  The error function is often used in probability and statistics. It integrates the normal distribution and gives the probability that a normally distributed random variable Y (with mean 0 and variance ½) falls into the range [−x, x]. The illustration below shows how the erfl function works: 