Streams

[wojpok]

This PR is a part of Pretty-printer PR #256 . This module have been separated for easier review. Interface is not complete and might be expanded in future. This version provides minimal required set of utilities to run pretty-printer.

[ppolesiuk]

The implementation looks solid. I have some minor comments regarding names of some functions, and documentation comments. A also would consider making type parameter X named for all functions through parameter mechanism.

[wojpok]

Changes:

• All functions are annotated
• changed the name of bind function to concatMap for compatibility with List module
• pureLazy is pure. Documentation reflects that
• Fixed documentation

Please, verify formatting style that I have used. Type annotation required me to break lines and I am not sure if this tyle is right.

[ppolesiuk]

As you have asked, I wrote some comments about formatting. And there is still one unresolved conversation from my previous review.

[Copilot]

Pull Request Overview

This PR introduces a new Stream module for lazy lists (also known as streams) to the standard library. This is part of the larger Pretty-printer PR #256 and provides the minimal required utilities for the pretty-printer implementation.

Key changes:

• Adds lib/Stream.fram with lazy stream implementation including constructors, transformations, and folds
• Adds comprehensive test coverage in test/stdlib/stdlib0007_Stream.fram
• Extends lib/Lazy.fram with pureRef function and improved pureLazy documentation for better integration with streams

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 8 comments.

File	Description
lib/Stream.fram	Implements lazy stream data structure with core operations (construction, mapping, filtering, folding) and proper laziness semantics
test/stdlib/stdlib0007_Stream.fram	Provides test coverage for stream operations including conversions, transformations, and edge cases
lib/Lazy.fram	Adds pure reference constructor and improves documentation for pureLazy to support stream implementation

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[ppolesiuk]

Now, looks better. I have some minor comments, and Copilot have found some spelling errors in the documentation comments.

[wojpok]

For consistency, I changed the pattern matching order. Nil / empty list is always the first case in pattern matching

[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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[Copilot]

The documentation states 'iteratively applying function f on previous results' but the implementation uses unfold which applies f to the seed/state, not to previous results. Consider clarifying as 'by repeatedly applying function f to a state value' or 'by unfolding a state with function f'.

Suggested change

	Initializes lazy stream by iteratively applying function `f` on previous results.
	This function may generate infinite stream.
	Initializes a lazy stream by repeatedly applying function `f` to a state value.
	This function may generate an infinite stream.

[ppolesiuk]

The PR is ready for merge. Thanks! The last comments from Copilot can be ignored, especially that on left to right direction of foldRight. It's a complete nonsense.