Implement Triangle

config.json

@@ -19,6 +19,7 @@
     "etl",
     "sieve",
     "rna-transcription",
+    "triangle",
     "roman-numerals",
     "hexadecimal",
     "grade-school",

exercises/triangle/.gitignore

@@ -0,0 +1,7 @@
+# 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 http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock

exercises/triangle/Cargo.toml

@@ -0,0 +1,3 @@
+[package]
+name = "triangle"
+version = "0.0.0"

exercises/triangle/HINTS.md

@@ -0,0 +1,11 @@
+# Triangle in Rust
+
+- [Result](https://doc.rust-lang.org/std/result/index.html)
+
+Implementation of this can take many forms. Here are some topics that may help you, depending on the approach you take.
+
+- [Enums](https://doc.rust-lang.org/book/enums.html)
+- [Traits](https://doc.rust-lang.org/book/traits.html)
+- [BTreeSet](https://doc.rust-lang.org/std/collections/btree_set/struct.BTreeSet.html)
+
+Or maybe you will come up with an approach that uses none of those!

exercises/triangle/example.rs

@@ -0,0 +1,38 @@
+use std::iter::FromIterator;
+use std::collections::BTreeSet;
+
+pub struct Triangle {
+    sides: [u16; 3],
+}
+
+impl Triangle {
+    #[cfg_attr(rustfmt, rustfmt_skip)]
+    fn valid_sides(&self) -> bool {
+        (self.sides.iter().all(|&s| s > 0)) &&
+            (self.sides[0] + self.sides[1] >= self.sides[2]) &&
+            (self.sides[1] + self.sides[2] >= self.sides[0]) &&
+            (self.sides[2] + self.sides[0] >= self.sides[1])
+    }
+
+    pub fn build(sides: [u16; 3]) -> Result<Self, ()> {
+        let t = Triangle { sides: sides };
+
+        if t.valid_sides() {
+            Ok(t)
+        } else {
+            Err(())
+        }
+    }
+
+    pub fn is_equilateral(&self) -> bool {
+        BTreeSet::from_iter(self.sides.iter()).len() == 1
+    }
+
+    pub fn is_isosceles(&self) -> bool {
+        BTreeSet::from_iter(self.sides.iter()).len() == 2
+    }
+
+    pub fn is_scalene(&self) -> bool {
+        BTreeSet::from_iter(self.sides.iter()).len() == 3
+    }
+}

exercises/triangle/float_example.rs

@@ -0,0 +1,55 @@
+use std::iter::FromIterator;
+use std::collections::BTreeSet;
+
+extern crate num;
+
+use num::Num;
+
+pub struct Triangle<T> {
+    sides: [T; 3],
+}
+
+impl<T: Num + PartialOrd + PartialEq + Copy> Triangle<T> {
+    #[cfg_attr(rustfmt, rustfmt_skip)]
+    fn valid_sides(&self) -> bool {
+        let z = self.sides[0] - self.sides[0];
+        (self.sides.iter().all(|&s| s > z)) &&
+            (self.sides[0] + self.sides[1] >= self.sides[2]) &&
+            (self.sides[1] + self.sides[2] >= self.sides[0]) &&
+            (self.sides[2] + self.sides[0] >= self.sides[1])
+    }
+
+    pub fn build(sides: [T; 3]) -> Result<Self, ()> {
+        let t = Triangle { sides: sides };
+
+        if t.valid_sides() {
+            Ok(t)
+        } else {
+            Err(())
+        }
+    }
+
+    pub fn is_equilateral(&self) -> bool {
+        let a = self.sides[0];
+        let b = self.sides[1];
+        let c = self.sides[2];
+
+        a == b && b == c
+    }
+
+    pub fn is_isosceles(&self) -> bool {
+        let a = self.sides[0];
+        let b = self.sides[1];
+        let c = self.sides[2];
+
+        (a == b && a != c) || (a == c && a != b) || (b == c && a != b)
+    }
+
+    pub fn is_scalene(&self) -> bool {
+        let a = self.sides[0];
+        let b = self.sides[1];
+        let c = self.sides[2];
+
+        a != b && a != c && b != c
+    }
+}

exercises/triangle/tests/triangle.rs

@@ -0,0 +1,170 @@
+extern crate triangle;
+
+use triangle::*;
+
+#[test]
+fn positive_length_sides_are_ok() {
+    let sides = [2, 2, 2];
+    let triangle = Triangle::build(sides);
+    assert!(triangle.is_ok());
+}
+
+#[test]
+#[ignore]
+fn zero_length_sides_are_illegal() {
+    let sides = [0, 0, 0];
+    let triangle = Triangle::build(sides);
+    assert!(triangle.is_err());
+}
+
+#[test]
+#[ignore]
+fn equilateral_triangles_have_equal_sides() {
+    let sides = [2, 2, 2];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(triangle.is_equilateral());
+    assert!(!triangle.is_isosceles());
+    assert!(!triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn larger_equilateral_triangles_have_equal_sides() {
+    let sides = [10, 10, 10];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(triangle.is_equilateral());
+    assert!(!triangle.is_isosceles());
+    assert!(!triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn isocseles_triangles_have_two_equal_sides_one() {
+    let sides = [3, 4, 4];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(triangle.is_isosceles());
+    assert!(!triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn isocseles_triangles_have_two_equal_sides_two() {
+    let sides = [4, 4, 3];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(triangle.is_isosceles());
+    assert!(!triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn isocseles_triangles_have_two_equal_sides_three() {
+    let sides = [4, 3, 4];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(triangle.is_isosceles());
+    assert!(!triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn isocseles_triangles_have_two_equal_sides_four() {
+    let sides = [4, 7, 4];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(triangle.is_isosceles());
+    assert!(!triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn scalene_triangle_has_no_equal_sides_one() {
+    let sides = [3, 4, 5];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(!triangle.is_isosceles());
+    assert!(triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn scalene_triangle_has_no_equal_sides_two() {
+    let sides = [5, 4, 6];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(!triangle.is_isosceles());
+    assert!(triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn scalene_triangle_has_no_equal_sides_three() {
+    let sides = [10, 11, 12];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(!triangle.is_isosceles());
+    assert!(triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn scalene_triangle_has_no_equal_sides_four() {
+    let sides = [5, 4, 2];
+    let triangle = Triangle::build(sides).unwrap();
+    assert!(!triangle.is_equilateral());
+    assert!(!triangle.is_isosceles());
+    assert!(triangle.is_scalene());
+}
+
+#[test]
+#[ignore]
+fn sum_of_two_sides_must_equal_or_exceed_the_remaining_side_one() {
+    let sides = [7, 3, 2];
+    let triangle = Triangle::build(sides);
+    assert!(triangle.is_err());
+}
+
+#[test]
+#[ignore]
+fn sum_of_two_sides_must_equal_or_exceed_the_remaining_side_two() {
+    let sides = [1, 1, 3];
+    let triangle = Triangle::build(sides);
+    assert!(triangle.is_err());
+}
+
+// Optional Tests
+//
+// Support Triangles with non-integer sides.
+//
+// You'll probably want to use the Num crate
+//
+// https://crates.io/crates/num
+//
+
+// #[test]
+// fn scalene_triangle_with_floating_point_sides() {
+//     let sides = [0.4, 0.6, 0.3];
+//     let triangle = Triangle::build(sides).unwrap();
+//     assert!(!triangle.is_equilateral());
+//     assert!(!triangle.is_isosceles());
+//     assert!(triangle.is_scalene());
+// }
+//
+// #[test]
+// fn equilateral_triangles_with_floating_point_sides() {
+//     let sides = [0.2, 0.2, 0.2];
+//     let triangle = Triangle::build(sides).unwrap();
+//     assert!(triangle.is_equilateral());
+//     assert!(!triangle.is_isosceles());
+//     assert!(!triangle.is_scalene());
+// }
+//
+// #[test]
+// fn isocseles_triangle_with_floating_point_sides() {
+//     let sides = [0.3, 0.4, 0.4];
+//     let triangle = Triangle::build(sides).unwrap();
+//     assert!(!triangle.is_equilateral());
+//     assert!(triangle.is_isosceles());
+//     assert!(!triangle.is_scalene());
+// }

problems.md

@@ -38,6 +38,7 @@ word-count |  hashmap, str vs string, chars, entry api
 etl |  btree
 sieve |  vector, map, while let (optional)
 rna-transcription |  match, struct, str vs string
+triangle | Math, Struct. Enum, Trait, Box -- depending on implementation
 roman-numerals |  mutable, results, loops, struct, traits
 hexadecimal |  Option, zip/fold/chars, map
 grade-school |  struct, entry api, Vec, Option