Built an app builder and other minor things

[kaka/rust-sdl-test.git] / src / common.rs

diff --git a/src/common.rs b/src/common.rs
index 6f000d8..f5ebb6e 100644 (file)
--- a/src/common.rs
+++ b/src/common.rs
@@ -1,4 +1,4 @@
-use std::ops::{Add, AddAssign};
+use std::ops::{Add, AddAssign, Mul};
 
 #[macro_export]
 macro_rules! point {
@@ -32,6 +32,25 @@ impl<T: AddAssign> AddAssign for Point2D<T> {
     }
 }
 
+#[derive(Default)]
+pub struct Rect<T> {
+    pub width: T,
+    pub height: T,
+}
+
+impl<T: Mul<Output=T> + Copy> Rect<T> {
+    #[allow(dead_code)]
+    pub fn area(&self) -> T {
+       self.width * self.height
+    }
+}
+
+impl<T> From<(T, T)> for Rect<T> {
+    fn from(item: (T, T)) -> Self {
+       Rect { width: item.0, height: item.1 }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -52,4 +71,11 @@ mod tests {
         a += point!(2, 2); // AddAssign
         assert_eq!(a, point!(3, 2));
     }
+
+    #[test]
+    fn area_for_rect_of_multipliable_type() {
+        let r: Rect<_> = (30, 20).into(); // the Into trait uses the From trait
+       assert_eq!(r.area(), 30 * 20);
+        // let a = Rect::from(("a".to_string(), "b".to_string())).area(); // this doesn't work, because area() is not implemented for String
+    }
 }