Promotion Rules

Return the ndarray data type with the smallest size and closest "kind" to which ndarray data types can be safely cast.

Usage

var promotionRules = require( '@stdlib/ndarray/promotion-rules' );

promotionRules( [dtype1, dtype2] )

If provided data types, returns the ndarray data type with the smallest size and closest "kind" to which ndarray data types can be safely cast.

var out = promotionRules( 'float32', 'uint32' );
// returns 'float64'

If a data type to which data types can be safely cast does not exist (or is not supported), the function returns -1.

var out = promotionRules( 'binary', 'generic' );
// returns -1

If not provided data types, the function returns a promotion table.

var out = promotionRules();
// returns {...}

var f32 = out[ 'float32' ];
// returns {...}

var rule = f32[ 'uint32' ];
// returns 'float64'

If provided an unrecognized or unsupported dtype, the function returns null.

var out = promotionRules( 'foo', 'generic' );
// returns null

Examples

var dtypes = require( '@stdlib/ndarray/dtypes' );
var promotionRules = require( '@stdlib/ndarray/promotion-rules' );

var DTYPES;
var dt1;
var dt2;
var dt;
var i;
var j;

// Get the list of supported ndarray data types:
DTYPES = dtypes();

// Print the promotion rule for each pair of ndarray data types...
for ( i = 0; i < DTYPES.length; i++ ) {
    dt1 = DTYPES[ i ];
    for ( j = 0; j < DTYPES.length; j++ ) {
        dt2 = DTYPES[ j ];
        dt = promotionRules( dt1, dt2 );
        console.log( '(%s, %s) => %s', dt1, dt2, dt );
    }
}

---

See Also

• @stdlib/ndarray/casting-modes: list of ndarray casting modes.
• @stdlib/ndarray/dtypes: list of ndarray data types.
• @stdlib/ndarray/safe-casts: return a list of ndarray data types to which a provided ndarray data type can be safely cast.