Merge pull request #163 from lamalex/recursion-in-rust

Add rust examples to 03_recursion

03_recursion/rust/01_countdown/.gitignore

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+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk

03_recursion/rust/01_countdown/Cargo.toml

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+[package]
+name = "countdown"
+version = "0.1.0"
+authors = ["Alexander Launi <alex.launi@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+num-traits = "0.2"

03_recursion/rust/01_countdown/src/main.rs

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+use std::ops::Sub;
+use std::fmt::Display;
+use num_traits::identities::One;
+use num_traits::identities::Zero;
+
+fn countdown<T: Display + One + Zero + Sub<Output = T>>(i: T) {
+    println!("{}", i);
+    if i.is_zero() {
+        return
+    }
+
+   countdown(i - T::one());
+}
+
+fn main() {
+    countdown(5);
+}

03_recursion/rust/02_greet/.gitignore

@@ -0,0 +1,10 @@
+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk

03_recursion/rust/02_greet/Cargo.toml

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+[package]
+name = "greet"
+version = "0.1.0"
+authors = ["Alexander Launi <alex.launi@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

03_recursion/rust/02_greet/src/main.rs

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+fn greet2(name: &str) {
+    println!("how are you {}?", name);
+}
+
+fn bye() {
+    println!("ok bye!");
+}
+
+fn greet(name: &str) {
+    println!("hello {}!", name);
+    greet2(name);
+    println!("getting ready to say bye...");
+    bye();
+}
+  
+fn main() {
+    greet("adit");
+}

03_recursion/rust/03_factorial/.gitignore

@@ -0,0 +1,10 @@
+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk

03_recursion/rust/03_factorial/Cargo.toml

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+[package]
+name = "factorial"
+version = "0.1.0"
+authors = ["Alexander Launi <alex.launi@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+num-traits = "0.2"

03_recursion/rust/03_factorial/src/main.rs

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+use std::ops::Sub;
+use std::fmt::Display;
+use num_traits::identities::One;
+
+fn fact<T: PartialOrd + PartialEq + One + Sub<Output = T> + Copy + Display>(x: T) -> T {
+    if x < T::one() {
+        panic!("Invalid number: {}", x);
+    } else if x.is_one() {
+        return T::one();
+    }
+
+    return x * fact(x - T::one());
+}
+
+fn main() {
+    println!("{}", fact(3));
+}