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gfirstIndexNotEqual

Returns the index of the first element in a strided array which is not equal to the corresponding element in another strided array.

Usage

var gfirstIndexNotEqual = require( '@stdlib/blas/ext/base/gfirst-index-not-equal' );

gfirstIndexNotEqual( N, x, strideX, y, strideY )

Returns the index of the first element in a strided array which is not equal to the corresponding element in another strided array.

var x = [ 0, 0, 1, 0 ];
var y = [ 0, 0, 0, 0 ];

var idx = gfirstIndexNotEqual( x.length, x, 1, y, 1 );
// returns 2

The function has the following parameters:

  • N: number of indexed elements.
  • x: first input Array or typed array.
  • strideX: stride length for x.
  • y: second input Array or typed array.
  • strideY: stride length for y.

If unable to find an element in x which is not equal to the corresponding element in y, the function returns -1.

var x = [ 0, 0, 0, 0 ];
var y = [ 0, 0, 0, 0 ];

var idx = gfirstIndexNotEqual( x.length, x, 1, y, 1 );
// returns -1

The N and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to compare every other element in x to every other element in y:

var x = [ 0, 0, 1, 0, 0, 0 ];
var y = [ 0, 0, 1, 0, 9, 0 ];

var idx = gfirstIndexNotEqual( 3, x, 2, y, 2 );
// returns 2

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array/float64' );

// Initial arrays...
var x0 = new Float64Array( [ 0, 0, 0, 1, 0, 0 ] );
var y0 = new Float64Array( [ 0, 0, 0, 0, 0, 0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var idx = gfirstIndexNotEqual( x1.length, x1, 1, y1, 1 );
// returns 2

gfirstIndexNotEqual.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )

Returns the index of the first element in a strided array which is not equal to the corresponding element in another strided array using alternative indexing semantics.

var x = [ 0, 0, 1, 0 ];
var y = [ 0, 0, 0, 0 ];

var idx = gfirstIndexNotEqual.ndarray( x.length, x, 1, 0, y, 1, 0 );
// returns 2

The function has the following additional parameters:

  • offsetX: starting index for x.
  • offsetY: starting index for y.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to compare the last three elements of x to the last three elements of y:

var x = [ 0, 0, 0, 1 ];
var y = [ 1, 0, 0, 0 ];

var idx = gfirstIndexNotEqual.ndarray( 3, x, 1, x.length-3, y, 1, y.length-3 );
// returns 2

Notes

  • If N <= 0, both functions return -1.
  • Both functions determine whether corresponding elements are equal using strict equality (i.e., the === operator). As a consequence, corresponding NaN elements are considered unequal (as NaN !== NaN always evaluates to true), while -0 and +0 are considered equal.
  • Both functions support array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array/base/accessor).

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var gfirstIndexNotEqual = require( '@stdlib/blas/ext/base/gfirst-index-not-equal' );

var x = discreteUniform( 10, -5, 5, {
    'dtype': 'generic'
});
console.log( x );

var y = discreteUniform( 10, -5, 5, {
    'dtype': 'generic'
});
console.log( y );

var idx = gfirstIndexNotEqual( x.length, x, 1, y, 1 );
console.log( idx );