feat: add `blas/ext/join-between` by headlessNode · Pull Request #11287 · stdlib-js/stdlib

headlessNode · 2026-04-03T20:25:44Z

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Resolves stdlib-js/metr-issue-tracker#238.

Description

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This pull request:

add blas/ext/join-between

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This pull request has the following related issues:

Resolves [RFC]: add blas/ext/join-between metr-issue-tracker#238

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Primarily written by Claude Code but with heavy back-and-forth fixing.

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stdlib-bot · 2026-04-03T20:28:58Z

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/join-between	$\color{red}453/459$ $\color{green}+98.69%$	$\color{red}44/47$ $\color{green}+93.62%$	$\color{green}5/5$ $\color{green}+100.00%$	$\color{red}453/459$ $\color{green}+98.69%$

The above coverage report was generated for the changes in this PR.

kgryte · 2026-04-04T07:12:07Z

lib/node_modules/@stdlib/blas/ext/join-between/lib/main.js

+* @param {string} [options.prefix=''] - prefix to prepend to each joined string
+* @param {string} [options.suffix=''] - suffix to append to each joined string


These should both be allowed to be ndarrays. What if I want to prefix each joined string with different prefixes? Ditto for suffix.

kgryte · 2026-04-04T07:16:42Z

lib/node_modules/@stdlib/blas/ext/join-between/lib/main.js

+	if ( opts.separators.length === 1 ) {
+		separators = broadcastScalar( opts.separators[ 0 ], 'generic', [ 1 ], order );
+	} else {
+		separators = new ndarray( 'generic', opts.separators, [ opts.separators.length ], [ 1 ], 0, order );
+	}


What's going on here? Why isn't separators being broadcast against the entire input array x? What if I want different separators for each row in a matrix?

kgryte · 2026-04-04T07:17:38Z

lib/node_modules/@stdlib/blas/ext/join-between/lib/main.js

+		separators = new ndarray( 'generic', opts.separators, [ opts.separators.length ], [ 1 ], 0, order );
+	}
+	// Perform the reduction:
+	unaryReduceStrided1d( dispatch, [ x, y ], opts.dims );


This is odd. Why are you doing it this way? A closure should not be necessary if you have done broadcasting correctly.

Using unaryReduceStrided1d and not *-dispatch and not -factory skips a bunch of validation logic that would have to be reimplemented here. That is not desirable. Ideally, we'd figure out a way to use the *-factory package.

Validation including acceptable dtypes. TL;DR: there is a lot currently incorrect with this implementation.

kgryte · 2026-04-04T07:18:16Z

lib/node_modules/@stdlib/blas/ext/join-between/lib/main.js

+	* @param {Array<Object>} arrays - ndarrays
+	* @returns {string} joined string
+	*/
+	function dispatch( arrays ) {


This function should not be necessary. prefix, suffix, and separators should all be passed down as auxiliary arrays via unaryReduceStrided1d, not via a closure like this.

Hmm...but I see that separators will be problematic here, as unaryReduceStrided1d assumes all ancillary arrays are 0D, while separators will always be 1D.

It's possible that we need only tweak unary-reduce-strided1d slightly here.

@kgryte I think two changes in unary-reduce-strided1d would unlock the factory approach:

Allow arrays with extra trailing dimensions here: https://github.com/stdlib-js/stdlib/blob/develop/lib/node_modules/%40stdlib/ndarray/base/unary-reduce-strided1d/lib/main.js#L380

Pass K here: https://github.com/stdlib-js/stdlib/blob/develop/lib/node_modules/%40stdlib/ndarray/base/unary-reduce-strided1d/lib/main.js#L428, and for array with more than K dimensions, preserved trailing dimensions instead of collapsing to 0d.

I believe the iteration code would work as is. Should I go ahead with these changes in unary-reduce-strided1d? and the binary-* counterpart as well?

kgryte

Left initial comments.

headlessNode added Feature Issue or pull request for adding a new feature. METR Pull request associated with the METR project. labels Apr 3, 2026

stdlib-bot added BLAS Issue or pull request related to Basic Linear Algebra Subprograms (BLAS). Needs Review A pull request which needs code review. labels Apr 3, 2026

headlessNode requested a review from kgryte April 3, 2026 20:29

github-actions bot mentioned this pull request Apr 4, 2026

[aw] No-Op Runs #11033

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kgryte added Needs Changes Pull request which needs changes before being merged. and removed Needs Review A pull request which needs code review. labels Apr 4, 2026

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feat: add `blas/ext/join-between`#11287

feat: add `blas/ext/join-between`#11287
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headlessNode:blas/nd-joinbetween

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		* @param {string} [options.prefix=''] - prefix to prepend to each joined string
		* @param {string} [options.suffix=''] - suffix to append to each joined string

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