Q Phrasebook

The phrasebook is a collection of q expressions used for common tasks.

Because q is a terse language, the phrasebook is a particularly useful tool for programmers. This collection of q expressions solves common problems and serves both as a library for coders and a set of problems for those learning the language.

Repository

This is an open-source collection, and a repository of community programming knowledge.

You can contribute to the project at kxcontrib/phrases. Or write to librarian@kx.com.

Genealogy

The q phrases derive originally from the FinnAPL Idiom Library, a legendary resource for vector programmers.

Iverson’s reboot of APL was the J programming language, where the idioms became phrases.

Eugene McDonnell ported the FinnAPL Idiom Library to the k language. A partial translation of that into q was hosted – as an extraordinarily long page – on the old wiki.

Kdb+ and the history of the Q Phrasebook

The k idiom list and its partial translation as the QIdioms page were exercises by experienced programmers who at the time were getting to know the respective languages.

The Q Phrasebook aims to fulfill their project of producing a q equivalent of the FinnAPL Idiom Library and the J Phrases.

Many of the original problems have the same solution in q. The numbering inherited from the ancestor lists has not been preserved. The phrases have been renumbered. The index to QIdioms maps old to new numbers.

Paint the town red

The meaning of an idiom is given by customary usage. It cannot be understood by analyzing the words in it.

For example, someone who paints the town red might not use paint of any color; but just goes out for a good time.

The Q Phrases are not idioms. They can be understood by analysis, and reward study. So phrases, not idioms.

That’s a phrase?

Some of the ‘phrases’ turn out to be just q operators or keywords. For example, Case structure is nothing but the Cond operator.

They are included here because, although they are elementary in q, readers coming from verbose languages might reasonably expect them to be at least a phrase.

phrases.q

Some forms, such as til count recur so frequently they have been included in the script phrases.q and used as parts of other phrases.