feat: add ndarray/base/scalar-dtype

Introduce a reusable package that resolves a default ndarray data type
from a scalar value, and update `ndarray/base/atleastnd` and
`ndarray/from-scalar` to consume it, removing duplicated logic.

Ref: #11002

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Kaushikgtm

lib/node_modules/@stdlib/ndarray/base/atleastnd/lib/main.js

@@ -21,10 +21,7 @@
 // MODULES //
 
 var isndarrayLike = require( '@stdlib/assert/is-ndarray-like' );
-var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
-var isComplexLike = require( '@stdlib/assert/is-complex-like' );
-var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
-var complexDataType = require( '@stdlib/complex/dtype' );
+var scalarDataType = require( '@stdlib/ndarray/base/scalar-dtype' );
 var broadcastScalar = require( '@stdlib/ndarray/base/broadcast-scalar' );
 var dims = require( '@stdlib/ndarray/base/ndims' );
 var defaults = require( '@stdlib/ndarray/defaults' );
@@ -40,9 +37,6 @@ var ones = require( '@stdlib/array/base/ones' );
 
 // VARIABLES //
 
-var DEFAULT_REAL = defaults.get( 'dtypes.real_floating_point' );
-var DEFAULT_CMPLX = defaults.get( 'dtypes.complex_floating_point' );
-var DEFAULT_BOOL = defaults.get( 'dtypes.boolean' );
 var ORDER = defaults.get( 'order' );
 
 
@@ -108,18 +102,7 @@ function atleastnd( ndims, arrays ) {
 			continue;
 		}
 		// For scalar values, resolve a corresponding ndarray data type...
-		if ( isNumber( v ) ) { // TODO: consider abstracting this logic to an `ndarray/base/scalar-dtype` (???) package, as this logic is found elsewhere (e.g., `ndarray/from-scalar`) and it would be good to avoid duplication, especially as we add support for more ndarray data types
-			dt = DEFAULT_REAL;
-		} else if ( isBoolean( v ) ) {
-			dt = DEFAULT_BOOL;
-		} else if ( isComplexLike( v ) ) {
-			dt = complexDataType( v );
-			if ( dt === null ) {
-				dt = DEFAULT_CMPLX;
-			}
-		} else {
-			dt = 'generic';
-		}
+		dt = scalarDataType( v );
 		out.push( broadcastScalar( v, dt, ones( ndims ), ORDER ) );
 	}
 	return out;

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/README.md

@@ -0,0 +1,77 @@
+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2026 The Stdlib Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+-->
+
+# scalarDataType
+
+> Resolve a default [ndarray][@stdlib/ndarray/ctor] data type from a scalar value.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var scalarDataType = require( '@stdlib/ndarray/base/scalar-dtype' );
+```
+
+#### scalarDataType( value )
+
+Resolves a default [ndarray][@stdlib/ndarray/ctor] data type from a scalar value.
+
+```javascript
+var dt = scalarDataType( 3.14 );
+// returns <string>
+
+dt = scalarDataType( 'beep' );
+// returns 'generic'
+```
+
+The function applies the following resolution rules:
+
+-   If `value` is a number, the function returns the default real-valued floating-point data type.
+-   If `value` is a boolean, the function returns the default boolean data type.
+-   If `value` is a complex number object of a known complex data type, the function returns the corresponding complex data type.
+-   If `value` is a complex number object of an unknown complex data type, the function returns the default complex-valued floating-point data type.
+-   For any other value, the function returns `'generic'`.
+
+</section>
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var Complex128 = require( '@stdlib/complex/float64/ctor' );
+var scalarDataType = require( '@stdlib/ndarray/base/scalar-dtype' );
+
+console.log( scalarDataType( 3.14 ) );
+console.log( scalarDataType( true ) );
+console.log( scalarDataType( new Complex128( 1.0, 2.0 ) ) );
+console.log( scalarDataType( 'beep' ) );
+```
+
+</section>
+
+<section class="links">
+
+[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/stdlib
+
+</section>

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/benchmark/benchmark.js

@@ -0,0 +1,57 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var bench = require( '@stdlib/bench' );
+var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
+var Complex128 = require( '@stdlib/complex/float64/ctor' );
+var pkg = require( './../package.json' ).name;
+var scalarDataType = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+	var values;
+	var dt;
+	var i;
+
+	values = [
+		3.14,
+		true,
+		new Complex128( 1.0, 2.0 ),
+		'beep'
+	];
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		dt = scalarDataType( values[ i % values.length ] );
+		if ( typeof dt !== 'string' ) {
+			b.fail( 'should return a string' );
+		}
+	}
+	b.toc();
+	if ( !isString( dt ) ) {
+		b.fail( 'should return a string' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/docs/repl.txt

@@ -0,0 +1,38 @@
+
+{{alias}}( value )
+    Resolves a default ndarray data type from a scalar value.
+
+    If `value` is a number, the function returns the default real-valued
+    floating-point data type.
+
+    If `value` is a boolean, the function returns the default boolean data
+    type.
+
+    If `value` is a complex number object of a known complex data type, the
+    function returns the corresponding complex data type.
+
+    If `value` is a complex number object of an unknown complex data type, the
+    function returns the default complex-valued floating-point data type.
+
+    For any other value, the function returns 'generic'.
+
+    Parameters
+    ----------
+    value: any
+        Scalar value.
+
+    Returns
+    -------
+    out: string
+        Data type.
+
+    Examples
+    --------
+    > var dt = {{alias}}( 3.14 )
+    <string>
+    > dt = {{alias}}( 'beep' )
+    'generic'
+
+    See Also
+    --------
+

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/docs/types/index.d.ts

@@ -0,0 +1,40 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+// TypeScript Version: 4.1
+
+/**
+* Resolves a default ndarray data type from a scalar value.
+*
+* @param value - scalar value
+* @returns data type
+*
+* @example
+* var dt = scalarDataType( 3.14 );
+* // returns <string>
+*
+* @example
+* var dt = scalarDataType( 'beep' );
+* // returns 'generic'
+*/
+declare function scalarDataType( value: any ): string;
+
+
+// EXPORTS //
+
+export = scalarDataType;

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/docs/types/test.ts

@@ -0,0 +1,34 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+import scalarDataType = require( './index' );
+
+
+// TESTS //
+
+// The function returns a string...
+{
+	scalarDataType( 3.14 ); // $ExpectType string
+	scalarDataType( 'beep' ); // $ExpectType string
+}
+
+// The compiler throws an error if the function is provided an unsupported number of arguments...
+{
+	scalarDataType(); // $ExpectError
+	scalarDataType( 3.14, 3 ); // $ExpectError
+}

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/examples/index.js

@@ -0,0 +1,27 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+var Complex128 = require( '@stdlib/complex/float64/ctor' );
+var scalarDataType = require( './../lib' );
+
+console.log( scalarDataType( 3.14 ) );
+console.log( scalarDataType( true ) );
+console.log( scalarDataType( new Complex128( 1.0, 2.0 ) ) );
+console.log( scalarDataType( 'beep' ) );

lib/node_modules/@stdlib/ndarray/base/scalar-dtype/lib/index.js

@@ -0,0 +1,43 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+/**
+* Resolve a default ndarray data type from a scalar value.
+*
+* @module @stdlib/ndarray/base/scalar-dtype
+*
+* @example
+* var scalarDataType = require( '@stdlib/ndarray/base/scalar-dtype' );
+*
+* var dt = scalarDataType( 3.14 );
+* // returns <string>
+*
+* dt = scalarDataType( 'beep' );
+* // returns 'generic'
+*/
+
+// MODULES //
+
+var main = require( './main.js' );
+
+
+// EXPORTS //
+
+module.exports = main;