# Kronecker Delta
> Evaluate the [Kronecker delta][kronecker-delta].
The [Kronecker delta][kronecker-delta] is defined as
## Usage
```javascript
var kroneckerDelta = require( '@stdlib/math/base/special/kronecker-delta' );
```
#### kroneckerDelta( i, j )
Evaluates the [Kronecker delta][kronecker-delta].
```javascript
var v = kroneckerDelta( 3.14, 3.14 );
// returns 1.0
v = kroneckerDelta( 3.14, 0.0 );
// returns 0.0
v = kroneckerDelta( NaN, 3.14 );
// returns NaN
v = kroneckerDelta( 3.14, NaN );
// returns NaN
v = kroneckerDelta( NaN, NaN );
// returns NaN
```
## Examples
```javascript
var linspace = require( '@stdlib/array/linspace' );
var kroneckerDelta = require( '@stdlib/math/base/special/kronecker-delta' );
var x = linspace( -1.0, 1.0, 101 );
var i;
for ( i = 0; i < x.length; i++ ) {
console.log( 'kronecker(%d,%d) = %d', x[ i ], 0.0, kroneckerDelta( x[ i ], 0.0 ) );
}
```
* * *
## C APIs
### Usage
```c
#include "stdlib/math/base/special/kronecker_delta.h
```
#### stdlib_base_kronecker_delta( i, j )
Evaluates the Kronecker delta.
```c
double v = stdlib_base_kronecker_delta( 3.0, 3.0 );
// returns 1.0
```
The function accepts the following arguments:
- **i**: `[in] double` input value.
- **j**: `[in] double` input value.
```c
double stdlib_base_kronecker_delta( const double i, const double j );
```
### Examples
```c
#include "stdlib/math/base/special/kronecker_delta.h"
#include
int main() {
double x[] = { 3.0, 4.0, 5.0, 5.0 };
double y;
int i;
for ( i = 0; i < 4; i += 2 ) {
y = stdlib_base_kronecker_delta( x[ i ], x[ i+1 ] );
printf( "kronecker_delta(%lf, %lf) = %lf\n", x[ i ], x[ i+1 ], y );
}
}
```
[kronecker-delta]: https://en.wikipedia.org/wiki/Kronecker_delta
