Improve AST evaluation efficiency by sharing functions.

tests/call_fn.rs

@@ -22,8 +22,7 @@ fn test_fn() -> Result<(), EvalAltResult> {
 fn test_call_fn() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
 
-    engine.consume(
-        true,
+    let ast = engine.compile(
         r"
             fn hello(x, y) {
                 x + y
@@ -31,14 +30,20 @@ fn test_call_fn() -> Result<(), EvalAltResult> {
             fn hello(x) {
                 x * 2
             }
-                ",
+            fn hello() {
+                42
+            }
+        ",
     )?;
 
-    let r: i64 = engine.call_fn("hello", (42 as INT, 123 as INT))?;
+    let r: i64 = engine.call_fn(&ast, "hello", (42 as INT, 123 as INT))?;
     assert_eq!(r, 165);
 
-    let r: i64 = engine.call_fn("hello", 123 as INT)?;
+    let r: i64 = engine.call_fn1(&ast, "hello", 123 as INT)?;
     assert_eq!(r, 246);
 
+    let r: i64 = engine.call_fn0(&ast, "hello")?;
+    assert_eq!(r, 42);
+
     Ok(())
 }