nushell/crates/nu-protocol/src/variable.rs

use crate::{Span, Type, Value};

#[derive(Clone, Debug)]
pub struct Variable {
    pub declaration_span: Span,
    pub ty: Type,
    pub mutable: bool,
    pub const_val: Option<Value>,
}

impl Variable {
    pub fn new(declaration_span: Span, ty: Type, mutable: bool) -> Variable {
        Self {
            declaration_span,
            ty,
            mutable,
            const_val: None,
        }
    }
}
Fix broken constants in scopes (#9679) 2023-07-13 21:02:05 +00:00			`use crate::{Span, Type, Value};`
Add support for var decl spans (#4787) 2022-03-09 09:42:19 +00:00
			`#[derive(Clone, Debug)]`
			`pub struct Variable {`
			`pub declaration_span: Span,`
			`pub ty: Type,`
Limited mutable variables (#7089) 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. 2022-11-11 06:51:08 +00:00			`pub mutable: bool,`
Fix broken constants in scopes (#9679) 2023-07-13 21:02:05 +00:00			`pub const_val: Option<Value>,`
Add support for var decl spans (#4787) 2022-03-09 09:42:19 +00:00			`}`

			`impl Variable {`
Limited mutable variables (#7089) 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. 2022-11-11 06:51:08 +00:00			`pub fn new(declaration_span: Span, ty: Type, mutable: bool) -> Variable {`
Add support for var decl spans (#4787) 2022-03-09 09:42:19 +00:00			`Self {`
			`declaration_span,`
			`ty,`
Limited mutable variables (#7089) 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. 2022-11-11 06:51:08 +00:00			`mutable,`
Fix broken constants in scopes (#9679) 2023-07-13 21:02:05 +00:00			`const_val: None,`
Add support for var decl spans (#4787) 2022-03-09 09:42:19 +00:00			`}`
			`}`
			`}`