Enum grafix_toolbox::uses::ops::ControlFlow1.55.0[−][src]

pub enum ControlFlow<B, C = ()> {
    Continue(C),
    Break(B),
}
Expand description

Used to tell an operation whether it should exit early or go on as usual.

This is used when exposing things (like graph traversals or visitors) where you want the user to be able to choose whether to exit early. Having the enum makes it clearer – no more wondering “wait, what did false mean again?” – and allows including a value.

Examples

Early-exiting from Iterator::try_for_each:

use std::ops::ControlFlow;

let r = (2..100).try_for_each(|x| {
    if 403 % x == 0 {
        return ControlFlow::Break(x)
    }

    ControlFlow::Continue(())
});
assert_eq!(r, ControlFlow::Break(13));

A basic tree traversal:

use std::ops::ControlFlow;

pub struct TreeNode<T> {
    value: T,
    left: Option<Box<TreeNode<T>>>,
    right: Option<Box<TreeNode<T>>>,
}

impl<T> TreeNode<T> {
    pub fn traverse_inorder<B>(&self, f: &mut impl FnMut(&T) -> ControlFlow<B>) -> ControlFlow<B> {
        if let Some(left) = &self.left {
            left.traverse_inorder(f)?;
        }
        f(&self.value)?;
        if let Some(right) = &self.right {
            right.traverse_inorder(f)?;
        }
        ControlFlow::Continue(())
    }
    fn leaf(value: T) -> Option<Box<TreeNode<T>>> {
        Some(Box::new(Self { value, left: None, right: None }))
    }
}

let node = TreeNode {
    value: 0,
    left: TreeNode::leaf(1),
    right: Some(Box::new(TreeNode {
        value: -1,
        left: TreeNode::leaf(5),
        right: TreeNode::leaf(2),
    }))
};
let mut sum = 0;

let res = node.traverse_inorder(&mut |val| {
    if *val < 0 {
        ControlFlow::Break(*val)
    } else {
        sum += *val;
        ControlFlow::Continue(())
    }
});
assert_eq!(res, ControlFlow::Break(-1));
assert_eq!(sum, 6);

Variants

Continue(C)

Move on to the next phase of the operation as normal.

Tuple Fields of Continue

0: C
Break(B)

Exit the operation without running subsequent phases.

Tuple Fields of Break

0: B

Implementations

🔬 This is a nightly-only experimental API. (control_flow_enum)

new API

Returns true if this is a Break variant.

Examples
#![feature(control_flow_enum)]
use std::ops::ControlFlow;

assert!(ControlFlow::<i32, String>::Break(3).is_break());
assert!(!ControlFlow::<String, i32>::Continue(3).is_break());
🔬 This is a nightly-only experimental API. (control_flow_enum)

new API

Returns true if this is a Continue variant.

Examples
#![feature(control_flow_enum)]
use std::ops::ControlFlow;

assert!(!ControlFlow::<i32, String>::Break(3).is_continue());
assert!(ControlFlow::<String, i32>::Continue(3).is_continue());
🔬 This is a nightly-only experimental API. (control_flow_enum)

new API

Converts the ControlFlow into an Option which is Some if the ControlFlow was Break and None otherwise.

Examples
#![feature(control_flow_enum)]
use std::ops::ControlFlow;

assert_eq!(ControlFlow::<i32, String>::Break(3).break_value(), Some(3));
assert_eq!(ControlFlow::<String, i32>::Continue(3).break_value(), None);
🔬 This is a nightly-only experimental API. (control_flow_enum)

new API

Maps ControlFlow<B, C> to ControlFlow<T, C> by applying a function to the break value in case it exists.

🔬 This is a nightly-only experimental API. (control_flow_enum)

new API

It’s frequently the case that there’s no value needed with Continue, so this provides a way to avoid typing (()), if you prefer it.

Examples
#![feature(control_flow_enum)]
use std::ops::ControlFlow;

let mut partial_sum = 0;
let last_used = (1..10).chain(20..25).try_for_each(|x| {
    partial_sum += x;
    if partial_sum > 100 { ControlFlow::Break(x) }
    else { ControlFlow::CONTINUE }
});
assert_eq!(last_used.break_value(), Some(22));
🔬 This is a nightly-only experimental API. (control_flow_enum)

new API

APIs like try_for_each don’t need values with Break, so this provides a way to avoid typing (()), if you prefer it.

Examples
#![feature(control_flow_enum)]
use std::ops::ControlFlow;

let mut partial_sum = 0;
(1..10).chain(20..25).try_for_each(|x| {
    if partial_sum > 100 { ControlFlow::BREAK }
    else { partial_sum += x; ControlFlow::CONTINUE }
});
assert_eq!(partial_sum, 108);

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

🔬 This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

🔬 This is a nightly-only experimental API. (try_trait_v2)

The type of the value produced by ? when not short-circuiting.

🔬 This is a nightly-only experimental API. (try_trait_v2)

The type of the value passed to FromResidual::from_residual as part of ? when short-circuiting. Read more

🔬 This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from its Output type. Read more

🔬 This is a nightly-only experimental API. (try_trait_v2)

Used in ? to decide whether the operator should produce a value (because this returned ControlFlow::Continue) or propagate a value back to the caller (because this returned ControlFlow::Break). Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

Should always be Self

The inverse inclusion map: attempts to construct self from the equivalent element of its superset. Read more

Checks if self is actually part of its subset T (and can be converted to it).

Use with care! Same as self.to_subset but without any property checks. Always succeeds.

The inclusion map: converts self to the equivalent element of its superset.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.