Return the ndarray data type with the smallest size and closest kind to which ndarray data types can be safely cast.
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> Return the ndarray [data type][@stdlib/ndarray/dtypes] with the smallest size and closest "kind" to which ndarray [data types][@stdlib/ndarray/dtypes] can be safely cast.
``bash`
npm install @stdlib/ndarray-promotion-rules
`javascript`
var promotionRules = require( '@stdlib/ndarray-promotion-rules' );
#### promotionRules( \[dtype1, dtype2] )
If provided [data types][@stdlib/ndarray/dtypes], returns the ndarray [data type][@stdlib/ndarray/dtypes] with the smallest size and closest "kind" to which ndarray [data types][@stdlib/ndarray/dtypes] can be safely cast.
`javascript`
var out = promotionRules( 'float32', 'uint32' );
// returns 'float64'
If a [data type][@stdlib/ndarray/dtypes] to which [data types][@stdlib/ndarray/dtypes] can be safely cast does not exist (or is not supported), the function returns -1.
`javascript`
var out = promotionRules( 'binary', 'generic' );
// returns -1
If not provided [data types][@stdlib/ndarray/dtypes], the function returns a promotion table.
`javascript
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.
`javascript`
var out = promotionRules( 'foo', 'generic' );
// returns null
`javascript
var cartesianProduct = require( '@stdlib/array-cartesian-product' );
var dtypes = require( '@stdlib/ndarray-dtypes' );
var unzip = require( '@stdlib/utils-unzip' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var promotionRules = require( '@stdlib/ndarray-promotion-rules' );
// Get the list of supported ndarray data types:
var dt = dtypes();
// Generate a list of data type pairs:
var pairs = cartesianProduct( dt, dt );
// Split the pairs into separate arrays:
var args = unzip( pairs );
// Print the promotion rule for each pair of ndarray data types:
logEachMap( '(%s, %s) => %s', args[ 0 ], args[ 1 ], promotionRules );
`
*
- [@stdlib/ndarray-casting-modes][@stdlib/ndarray/casting-modes]: list of ndarray casting modes.
- [@stdlib/ndarray-dtypes][@stdlib/ndarray/dtypes]: list of ndarray data types.
- [@stdlib/ndarray-safe-casts][@stdlib/ndarray/safe-casts]: return a list of ndarray data types to which a provided ndarray data type can be safely cast.
*
This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].
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