Add docs for auto-currying.

tests/closures.rs

@@ -0,0 +1,60 @@
+#![cfg(not(feature = "no_function"))]
+use rhai::{Dynamic, Engine, EvalAltResult, FnPtr, Module, INT};
+use std::any::TypeId;
+
+#[test]
+fn test_fn_ptr_curry_call() -> Result<(), Box<EvalAltResult>> {
+    let mut module = Module::new();
+
+    module.set_raw_fn(
+        "call_with_arg",
+        &[TypeId::of::<FnPtr>(), TypeId::of::<INT>()],
+        |engine: &Engine, lib: &Module, args: &mut [&mut Dynamic]| {
+            let fn_ptr = std::mem::take(args[0]).cast::<FnPtr>();
+            fn_ptr.call_dynamic(engine, lib, None, [std::mem::take(args[1])])
+        },
+    );
+
+    let mut engine = Engine::new();
+    engine.load_package(module.into());
+
+    #[cfg(not(feature = "no_object"))]
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let addition = |x, y| { x + y };
+                let curried = addition.curry(2);
+
+                call_with_arg(curried, 40)
+            "#
+        )?,
+        42
+    );
+
+    Ok(())
+}
+
+#[test]
+#[cfg(not(feature = "no_capture"))]
+fn test_closures() -> Result<(), Box<EvalAltResult>> {
+    let engine = Engine::new();
+
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let x = 8;
+
+                let res = |y, z| {
+                    let w = 12;
+
+                    return (|| x + y + z + w).call();
+                }.curry(15).call(2);
+
+                res + (|| x - 3).call()
+            "#
+        )?,
+        42
+    );
+
+    Ok(())
+}