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Add reference_cycles example

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This commit is contained in:
Timothy Warren 2019-02-05 11:23:56 -05:00
parent fcd4ecceb1
commit 971140b6ff
5 changed files with 144 additions and 39 deletions
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1
.idea/misc.xml generated
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@ -27,6 +27,7 @@
<cargoProject FILE="$PROJECT_DIR$/smart_pointers/Cargo.toml" />
<cargoProject FILE="$PROJECT_DIR$/reference_counting/Cargo.toml" />
<cargoProject FILE="$PROJECT_DIR$/interior_mutability/Cargo.toml" />
<cargoProject FILE="$PROJECT_DIR$/reference_cycles/Cargo.toml" />
</component>
<component name="ComposerJsonPluginSettings">
<unboundedVersionInspectionSettings>

5
.idea/rust.iml generated
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@ -110,6 +110,10 @@
<sourceFolder url="file://$MODULE_DIR$/interior_mutability/examples" isTestSource="false" />
<sourceFolder url="file://$MODULE_DIR$/interior_mutability/tests" isTestSource="true" />
<sourceFolder url="file://$MODULE_DIR$/interior_mutability/benches" isTestSource="true" />
<sourceFolder url="file://$MODULE_DIR$/reference_cycles/src" isTestSource="false" />
<sourceFolder url="file://$MODULE_DIR$/reference_cycles/examples" isTestSource="false" />
<sourceFolder url="file://$MODULE_DIR$/reference_cycles/tests" isTestSource="true" />
<sourceFolder url="file://$MODULE_DIR$/reference_cycles/benches" isTestSource="true" />
<excludeFolder url="file://$MODULE_DIR$/add/add-one/target" />
<excludeFolder url="file://$MODULE_DIR$/add/adder/target" />
<excludeFolder url="file://$MODULE_DIR$/adder/target" />
@ -130,6 +134,7 @@
<excludeFolder url="file://$MODULE_DIR$/modules/target" />
<excludeFolder url="file://$MODULE_DIR$/rectangles/target" />
<excludeFolder url="file://$MODULE_DIR$/reference_counting/target" />
<excludeFolder url="file://$MODULE_DIR$/reference_cycles/target" />
<excludeFolder url="file://$MODULE_DIR$/references/target" />
<excludeFolder url="file://$MODULE_DIR$/scope/target" />
<excludeFolder url="file://$MODULE_DIR$/slices/target" />

72
.idea/workspace.xml generated
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@ -5,7 +5,6 @@
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@ -15,24 +14,11 @@
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@ -108,6 +94,7 @@
<option value="$PROJECT_DIR$/smart_pointers/src/main.rs" />
<option value="$PROJECT_DIR$/interior_mutability/src/lib.rs" />
<option value="$PROJECT_DIR$/reference_counting/src/main.rs" />
<option value="$PROJECT_DIR$/reference_cycles/src/main.rs" />
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@ -141,12 +128,12 @@
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<item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
<item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
<item name="reference_counting" type="9f88c78c:ScopeViewTreeModel$FileNode" />
<item name="reference_cycles" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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<path>
<item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
<item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
<item name="reference_counting" type="9f88c78c:ScopeViewTreeModel$FileNode" />
<item name="reference_cycles" type="9f88c78c:ScopeViewTreeModel$FileNode" />
<item name="src" type="9f88c78c:ScopeViewTreeModel$FileNode" />
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@ -180,7 +167,7 @@
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@ -208,7 +195,7 @@
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<component name="RunManager" selected="Cargo Command.Run reference_counting">
<component name="RunManager" selected="Cargo Command.Run reference_cycles">
<configuration name="&lt;template&gt;" type="TestNG" default="true" selected="false">
<option name="MAIN_CLASS_NAME" />
<option name="VM_PARAMETERS" value="-ea" />
@ -237,6 +224,16 @@
<envs />
<method v="2" />
</configuration>
<configuration name="Run reference_cycles" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
<option name="channel" value="DEFAULT" />
<option name="command" value="run --package reference_cycles --bin reference_cycles" />
<option name="allFeatures" value="false" />
<option name="nocapture" value="false" />
<option name="backtrace" value="SHORT" />
<option name="workingDirectory" value="file://$PROJECT_DIR$/reference_cycles" />
<envs />
<method v="2" />
</configuration>
<configuration name="Run smart_pointers" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
<option name="channel" value="DEFAULT" />
<option name="command" value="run --package smart_pointers --bin smart_pointers" />
@ -247,16 +244,6 @@
<envs />
<method v="2" />
</configuration>
<configuration name="Test lib::tests (1)" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
<option name="channel" value="DEFAULT" />
<option name="command" value="test --package minigrep_v2 --lib tests" />
<option name="allFeatures" value="false" />
<option name="nocapture" value="false" />
<option name="backtrace" value="SHORT" />
<option name="workingDirectory" value="file://$PROJECT_DIR$/minigrep_v2" />
<envs />
<method v="2" />
</configuration>
<configuration name="Test lib::tests" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
<option name="channel" value="DEFAULT" />
<option name="command" value="test --package interior_mutability --lib tests" />
@ -286,11 +273,11 @@
</configuration>
<recent_temporary>
<list>
<item itemvalue="Cargo Command.Run reference_cycles" />
<item itemvalue="Cargo Command.Run reference_counting" />
<item itemvalue="Cargo Command.Test lib::tests" />
<item itemvalue="Cargo Command.Test tests::it_sends_an_over_75_percent_warning_message" />
<item itemvalue="Cargo Command.Run smart_pointers" />
<item itemvalue="Cargo Command.Test lib::tests (1)" />
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@ -330,8 +317,8 @@
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@ -339,7 +326,7 @@
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@ -749,9 +736,16 @@
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@ -760,10 +754,10 @@
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<entry file="file://$PROJECT_DIR$/reference_counting/src/main.rs">
<entry file="file://$PROJECT_DIR$/reference_cycles/src/main.rs">
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7
reference_cycles/Cargo.toml Normal file
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@ -0,0 +1,7 @@
[package]
name = "reference_cycles"
version = "0.1.0"
authors = ["Timothy Warren <twarren@nabancard.com>"]
edition = "2018"
[dependencies]

98
reference_cycles/src/main.rs Normal file
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@ -0,0 +1,98 @@
use std::rc::{Rc, Weak};
use std::cell::RefCell;
use List::{Cons, Nil};
#[derive(Debug)]
enum List {
Cons(i32, RefCell<Rc<List>>),
Nil,
}
impl List {
fn tail(&self) -> Option<&RefCell<Rc<List>>> {
match self {
Cons(_, item) => Some(item),
Nil => None,
}
}
}
fn cycle_example() {
let a = Rc::new(Cons(5, RefCell::new(Rc::new(Nil))));
println!("a initial rc count = {}", Rc::strong_count(&a));
println!("a next item = {:?}", a.tail());
let b = Rc::new(Cons(10, RefCell::new(Rc::clone(&a))));
println!("a rc count after b creation = {}", Rc::strong_count(&a));
println!("b initial rc count = {}", Rc::strong_count(&b));
println!("b next item = {:?}", b.tail());
if let Some(link) = a.tail() {
*link.borrow_mut() = Rc::clone(&b);
}
println!("b rc count after changing a = {}", Rc::strong_count(&b));
println!("a rc count after changing a = {}", Rc::strong_count(&a));
// Uncomment the next line to see that we have a cycle;
// it will overflow the stack
// println!("a next item = {:?}", a.tail());
}
#[derive(Debug)]
struct Node {
value: i32,
parent: RefCell<Weak<Node>>,
children: RefCell<Vec<Rc<Node>>>,
}
fn weakref_example() {
let leaf = Rc::new(Node {
value: 3,
parent: RefCell::new(Weak::new()),
children: RefCell::new(vec![]),
});
println!(
"leaf strong = {}, weak = {}",
Rc::strong_count(&leaf),
Rc::weak_count(&leaf),
);
{
let branch = Rc::new(Node {
value: 5,
parent: RefCell::new(Weak::new()),
children: RefCell::new(vec![Rc::clone(&leaf)]),
});
*leaf.parent.borrow_mut() = Rc::downgrade(&branch);
println!(
"branch strong = {}, weak = {}",
Rc::strong_count(&branch),
Rc::weak_count(&branch),
);
println!(
"leaf strong = {}, weak = {}",
Rc::strong_count(&leaf),
Rc::weak_count(&leaf),
);
}
println!("leaf parent = {:?}", leaf.parent.borrow().upgrade());
println!(
"leaf strong = {}, weak = {}",
Rc::strong_count(&leaf),
Rc::weak_count(&leaf),
);
}
fn main() {
cycle_example();
weakref_example();
}