# Swift - erf() Function

The Swift erf() function returns the error function of the argument. The error function of x is defined as:

Error functions usually occur in probability, statistics and partial differential equation describing diffusion.

### Syntax

In Foundation framework, it is defined as follows:

```public func erf(_ x: CGFloat) -> CGFloat
public func erf(_ x: Float) -> Float
public func erf(_ x: Float80) -> Float80
public func erf(_ __x: Double) -> Double
```

### Parameters

 `x` Specify the value.

### Return Value

Returns the error function of the argument.

### Example:

In the example below, erf() function returns the error function of the given value.

```import Foundation

print("erf(-2.0) = \(erf(-2.0))")
print("erf(-1.0) = \(erf(-1.0))")
print("erf(0.0) = \(erf(0.0))")
print("erf(1.0) = \(erf(1.0))")
print("erf(2.0) = \(erf(2.0))")
```

The output of the above code will be:

```erf(-2.0) = -0.9953222650189527
erf(-1.0) = -0.8427007929497149
erf(0.0) = 0.0
erf(1.0) = 0.8427007929497149
erf(2.0) = 0.9953222650189527
```

❮ Swift Math Functions

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