This adds support for (limited) mutable variables. Mutable variables are created with mut much the same way immutable variables are made with let.
Mutable variables allow mutation via the assignment operator (=).
❯ mut x = 100
❯ $x = 200
❯ print $x
200
Mutable variables are limited in that they're only tended to be used in the local code block. Trying to capture a local variable will result in an error:
❯ mut x = 123; {|| $x }
Error: nu::parser::expected_keyword (link)
× Capture of mutable variable.
The intent of this limitation is to reduce some of the issues with mutable variables in general: namely they make code that's harder to reason about. By reducing the scope that a mutable variable can be used it, we can help create local reasoning about them.
Mutation can occur with fields as well, as in this case:
❯ mut y = {abc: 123}
❯ $y.abc = 456
❯ $y
On a historical note: mutable variables are something that we resisted for quite a long time, leaning as much as we could on the functional style of pipelines and dataflow. That said, we've watched folks struggle to work with reduce as an approximation for patterns that would be trivial to express with local mutation. With that in mind, we're leaning towards the happy path.
* Add source-env test for dynamic path
* Use correct module ID for env overlay imports
* Remove parser check from "overlay list"
It would cause unnecessary errors from some inner scope if some
overlay module was also defined in some inner scope.
* Restore Cargo.lock back
* Remove comments
* attempts to add `div` math operator
* allows `//` to be used too
* fmt:
* clippy issue
* returns appropriate type
* returns appropriate type 2
* fmt
* ensure consistency; rename to `fdiv`
* Update parser.rs
* Initial implementation of ordered call args
* Run cargo fmt
* Fix some clippy lints
* Add positional len and nth
* Cargo fmt
* Remove more old nth calls
* Good ole rustfmt
* Add named len
Co-authored-by: Hristo Filaretov <h.filaretov@protonmail.com>
* Add 'expor env' dummy command
* (WIP) Abstract away module exportables as Overlay
* Switch to Overlays for use/hide
Works for decls only right now.
* Fix passing import patterns of hide to eval
* Simplify use/hide of decls
* Add ImportPattern as Expr; Add use env eval
Still no parsing of "export env" so I can't test it yet.
* Refactor export parsing; Add InternalError
* Add env var export and activation; Misc changes
Now it is possible to `use` env var that was exported from a module.
This commit also adds some new errors and other small changes.
* Add env var hiding
* Fix eval not recognizing hidden decls
Without this change, calling `hide foo`, the evaluator does not know
whether a custom command named "foo" was hidden during parsing,
therefore, it is not possible to reliably throw an error about the "foo"
name not found.
* Add use/hide/export env var tests; Cleanup; Notes
* Ignore hide env related tests for now
* Fix main branch merge mess
* Fixed multi-word export def
* Fix hiding tests on Windows
* Remove env var hiding for now
