bitart: Complete builder pattern to allow changing parameters

Change expression depth to 4

src/bin/bitart/expression.rs

@@ -270,11 +270,7 @@ pub struct RandomExpressionBuilder {
     depth: usize,
 }
 impl RandomExpressionBuilder {
-    pub fn build<R: Rng>(rng: &mut R) -> Expression {
-        let builder = Self::new();
-        builder.build_binary(rng, builder.depth)
-    }
-    fn new() -> RandomExpressionBuilder {
+    pub fn new() -> RandomExpressionBuilder {
         // Default values
         let unary_rate = 0.3;
         let variable_rate = 0.5;
@@ -287,6 +283,9 @@ impl RandomExpressionBuilder {
             depth,
         }
     }
+    pub fn build<R: Rng>(&self, rng: &mut R) -> Expression {
+        self.build_binary(rng, self.depth)
+    }
     fn build_recursive<R: Rng>(&self, rng: &mut R, depth: usize, left: bool) -> Expression {
         if depth == 0 {
             self.build_leaf(rng, left)
@@ -315,4 +314,25 @@ impl RandomExpressionBuilder {
         let arg1 = self.build_recursive(rng, depth - 1, false);
         binary_operation(op, arg0, arg1)
     }
+
+    #[allow(unused)]
+    pub fn unary_rate(mut self, unary_rate: f64) -> Self {
+        self.unary_rate = unary_rate;
+        self
+    }
+    #[allow(unused)]
+    pub fn variable_rate(mut self, variable_rate: f64) -> Self {
+        self.variable_rate = variable_rate;
+        self
+    }
+    #[allow(unused)]
+    pub fn max_literal(mut self, max_literal: i64) -> Self {
+        self.max_literal = max_literal;
+        self
+    }
+    #[allow(unused)]
+    pub fn depth(mut self, depth: usize) -> Self {
+        self.depth = depth;
+        self
+    }
 }

src/bin/bitart/main.rs

@@ -118,6 +118,8 @@ fn main() -> std::io::Result<()> {
     let mut old_board = Board::with(Color::black(), bbox, |_p| Square::Uncommon);
     let mut new_board = Board::with(Color::black(), bbox, |_p| Square::Uncommon);
 
+    let builder = RandomExpressionBuilder::new().depth(4);
+
     let mut time_count = frame_time_count;
     loop {
         if time_count >= frame_time_count {
@@ -129,7 +131,7 @@ fn main() -> std::io::Result<()> {
 
             // Pick a random expression.
             loop {
-                let expression = RandomExpressionBuilder::build(&mut rng);
+                let expression = builder.build(&mut rng);
                 let values = Array2d::with(bbox, |p| {
                     let x = x0 + xk * p.x();
                     let y = y0 + yk * p.y();