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.
- Custom commands are true for builtin and custom
- Add classification as external command
- Specify wildcard in keyword: keyword is true for builtin and keyword
* Fix ignore-errors for select
* fix Value::List match
* fix invalid rows
* add tests
* fix ListStream match
* add one more test for ListStream
* add more tests
* tweak words
* Add failing test that list of ints and floats is List<Number>
* Start defining subtype relation
* Make it possible to declare input and output types for commands
- Enforce them in tests
* Declare input and output types of commands
* Add formatted signatures to `help commands` table
* Revert SyntaxShape::Table -> Type::Table change
* Revert unnecessary derive(Hash) on SyntaxShape
Co-authored-by: JT <547158+jntrnr@users.noreply.github.com>
Allows use of slightly optimized variants that check if they have to use
the heavier vte parser. Tries to avoid unnnecessary allocations. Initial
performance characteristics proven out in #4378.
Also reduces boilerplate with right-ward drift.
* fix: fixcd
try to fix
Log: try to fix the bug with can enter a permisson error fold
* change wording
* fat
* fmt
Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>
* make format filesize more flexible
* make code simpler
* finish refactor on bytes commands
* finish refactor on str commands
* fimplify code
* rename from column_paths to cell_paths
* fix: ✨ "saner" default for mv
fixes#6747
As highlighted in the issue, the default behavior of nu currently
is to overwrite the destination file without notice.
This is not a "standard" expectation users that want this behavior
can create a dedicated alias.
* fix: 📝 edit the comment
* fix: ✨ updated the tests
* fix: 🚧 use --force for case test
Fixes#6895
Warning: `Iterator::map_while` does not return a `FusedIterator`!
Depending on the consuming adaptor or code (e.g. for loop) the iteration
may be stopped but this is not guaranteed.
Adds a test example but Examples handle iterators like
`FusedIterator` and thus don't catch the regression
Cleanup the message on another test
