Add a color terminal renderer

Cargo.toml

@@ -7,3 +7,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+ansi_term = "0.12"

examples/coremem.rs

@@ -1,5 +1,5 @@
 use coremem::SimState;
-use coremem::render::NumericTermRenderer;
+use coremem::render::ColorTermRenderer;
 use coremem::consts;
 use std::{thread, time};
 
@@ -12,7 +12,7 @@ fn main() {
     state.impulse_b(15, 1.0/consts::C);
     state.impulse_e(15, 1.0);
     loop {
-        NumericTermRenderer.render(&state);
+        ColorTermRenderer.render(&state);
         state.step();
         thread::sleep(time::Duration::from_millis(100));
     }

src/render.rs

@@ -1,3 +1,5 @@
+use ansi_term::Color::RGB;
+use crate::consts;
 use crate::SimState;
 
 pub struct NumericTermRenderer;
@@ -15,3 +17,23 @@ impl NumericTermRenderer {
         print!("\n");
     }
 }
+
+pub struct ColorTermRenderer;
+
+fn clamp(v: f32, range: f32) -> f32 {
+    v.min(range).max(-range)
+}
+
+impl ColorTermRenderer {
+    pub fn render(&self, state: &SimState) {
+        let square = "█";
+        for cell in state.cells() {
+            let b_value = clamp(cell.by() * consts::C * 128.0, 255.0);
+            let b_color = RGB(0, b_value.max(0.0) as _, b_value.abs() as _);
+            let e_value = clamp(cell.ez() * 128.0, 255.0);
+            let e_color = RGB(e_value.abs() as _, e_value.max(0.0) as _, 0);
+            print!("{}{}", e_color.paint(square), b_color.paint(square));
+        }
+        print!("\n");
+    }
+}