[thelazydogsback]

Some of this reminds of me a combination Icon and Mozart. (And happened to just come across my old Icon book a few days ago.)

Maybe the backtracking concepts are "too built in?" - e.g., (1|2) is not a first-class/reified "amb" object, right? - so if I want to introduce a different search than depth-first backtracking (breadth, dependency-directed), etc., I couldn't directly.

Seems like there could be some confusion between multiple, backtracked values and actual sequences -- this often leads to sub-optimal/confusing Prolog code as well, deciding when you have an explicit control structure vs. backtrack, when to "harden" results using setOf/bagOf/findAll, etc.

[mncharity]

Can anyone speak to this for Icon?

For context, Prolog had a culture of "the built-in search is less than wonderful... but good for crafting a problem-appropriate search". II(fuzzily)RC, Mozart/Oz decoupled nondeterministic code (explicit amb, spelled "dis") specification from search, and allowed managing search over nested spaces of unification constraints and threads. With (very fuzzy) less use of backtrack-driven implicit sequences than in Prolog? I so don't remember Icon.

Curiously, https://www2.cs.arizona.edu/icon/books.htm includes a "newish" (2010) book, "Icon Programming for Humanists".

[cryptonector]

In Icon a function ("procedure") can: fail, return a value, or "suspend" (yield) a value (and then again and again). The difference between returning and suspending being that a generator that returns cannot be resumed again. That difference was needed (IIRC) because the alternative would be to end the generator with failure, which could be confused with failure in a boolean sense. jq gets this better by saying that a function can produce zero, one, or more values (just like Verse), but unlike Verse, jq does have booleans.

I prefer the jq approach to the Icon approach, which I think means I am suspicious of this aspect of Verse :)

Also, boolean values are inherently useful, and while checking that an expression is empty or not is a boolean predicate, it should be a predicate that produces a boolean value. Otherwise if we have no boolean values then we shouldn't have integer values either and just go back to the Lambda Calculus!

[Tarean]

I was wondering if they are planning to use some datalog-style compilation strategy, where all choices are dumped into b-trees and nesting is replaced by indexed tables which are joined.

But I think mixing this with unification vars is sort of an open research problem?

Plus Haskell had a `data-parallel` mode which used a similar compilation strategy. It was dropped for being very complex and having virtually no users. Plus using too much broadcasting and compiling higher order functions into vectorized code had a serious performance tax.