2 commits

Author	SHA1	Message	Date
Darren Schroeder	adb99938f7	rename unfold to generate (#10770) ... # Description This PR renames the `unfold` command to `generate`. closes #10760 # User-Facing Changes <!-- List of all changes that impact the user experience here. This helps us keep track of breaking changes. --> # Tests + Formatting <!-- Don't forget to add tests that cover your changes. Make sure you've run and fixed any issues with these commands: - `cargo fmt --all -- --check` to check standard code formatting (`cargo fmt --all` applies these changes) - `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used` to check that you're using the standard code style - `cargo test --workspace` to check that all tests pass (on Windows make sure to [enable developer mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging)) - `cargo run -- -c "use std testing; testing run-tests --path crates/nu-std"` to run the tests for the standard library > **Note** > from `nushell` you can also use the `toolkit` as follows > ```bash > use toolkit.nu # or use an `env_change` hook to activate it automatically > toolkit check pr > ``` --> # After Submitting <!-- If your PR had any user-facing changes, update [the documentation](https://github.com/nushell/nushell.github.io) after the PR is merged, if necessary. This will help us keep the docs up to date. -->	2023-10-19 09:30:34 -05:00
Hudson Clark	fa2e6e5d53	feat: Add unfold command (#10489) ... <!-- if this PR closes one or more issues, you can automatically link the PR with them by using one of the [*linking keywords*](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword), e.g. - this PR should close #xxxx - fixes #xxxx you can also mention related issues, PRs or discussions! --> # Description <!-- Thank you for improving Nushell. Please, check our [contributing guide](../CONTRIBUTING.md) and talk to the core team before making major changes. Description of your pull request goes here. **Provide examples and/or screenshots** if your changes affect the user experience. --> > [!NOTE] > This PR description originally used examples where the `generator` closure returned a list. It has since been updated to use records instead. The `unfold` command allows users to dynamically generate streams of data. The stream is generated by repeatedly invoking a `generator` closure. The `generator` closure accepts a single argument and returns a record containing two optional keys: 'out' and 'next'. Each invocation, the 'out' value, if present, is added to the stream. If a 'next' key is present, it is used as the next argument to the closure, otherwise generation stops. The name "unfold" is borrowed from other functional-programming languages. Whereas `fold` (or `reduce`) takes a stream of values and outputs a single value, `unfold` takes a single value and outputs a stream of values. ### Examples A common example of using `unfold` is to generate a fibbonacci sequence. See [here](6ffdac103c/src/sources.rs (L65)) for an example of this in rust's `itertools`. ```nushell > unfold [0, 1] {|fib| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} } | first 10 ───┬──── 0 │ 0 1 │ 1 2 │ 1 3 │ 2 4 │ 3 5 │ 5 6 │ 8 7 │ 13 8 │ 21 9 │ 34 ───┴──── ``` This command is particularly useful when consuming paginated APIs, like Github's. Previously, nushell users might use a loop and buffer responses into a list, before returning all responses at once. However, this behavior is not desirable if the result result is very large. Using `unfold` avoids buffering and allows subsequent pipeline stages to use the data concurrently, as it's being fetched. #### Before ```nushell mut pages = [] for page in 1.. { let resp = http get ( { scheme: https, host: "api.github.com", path: "/repos/nushell/nushell/issues", params: { page: $page, per_page: $PAGE_SIZE } } | url join) $pages = ($pages | append $resp) if ($resp | length) < $PAGE_SIZE { break } } $pages ``` #### After ```nu unfold 1 {|page| let resp = http get ( { scheme: https, host: "api.github.com", path: "/repos/nushell/nushell/issues", params: { page: $page, per_page: $PAGE_SIZE } } | url join) if ($resp | length) < $PAGE_SIZE { {out: $resp} } else { {out: $resp, next: ($page + 1)} } } ``` # User-Facing Changes <!-- List of all changes that impact the user experience here. This helps us keep track of breaking changes. --> - An `unfold` generator is added to the default context. # Tests + Formatting <!-- Don't forget to add tests that cover your changes. Make sure you've run and fixed any issues with these commands: - `cargo fmt --all -- --check` to check standard code formatting (`cargo fmt --all` applies these changes) - `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used` to check that you're using the standard code style - `cargo test --workspace` to check that all tests pass (on Windows make sure to [enable developer mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging)) - `cargo run -- -c "use std testing; testing run-tests --path crates/nu-std"` to run the tests for the standard library > **Note** > from `nushell` you can also use the `toolkit` as follows > ```bash > use toolkit.nu # or use an `env_change` hook to activate it automatically > toolkit check pr > ``` --> # After Submitting <!-- If your PR had any user-facing changes, update [the documentation](https://github.com/nushell/nushell.github.io) after the PR is merged, if necessary. This will help us keep the docs up to date. --> Given the complexity of the `generator` closure's return value, it would be good to document the semantics of `unfold` and provide some in-depth examples showcasing what it can accomplish.	2023-09-30 09:08:06 -05:00