Add Node::eval_number[_with_context] methods

Relates to #20

CHANGELOG.md

@@ -9,6 +9,7 @@
  * Make the `TupleType` alias public
  * Add the `ValueType` enum that represents the type of a value for easier comparisons and matchings
  * Add `EvalexprResult<T>` type that uses the `EvalexprError` type (renamed from `Error`)
+ * Add `Node::eval_number` and `Node::eval_number_with_context` to evaluate to int or float and silently converting to float
 
 ### Removed
 

src/tree/mod.rs

@@ -94,6 +94,19 @@ impl Node {
         }
     }
 
+    /// Evaluates the operator tree rooted at this node into a float with an the given context.
+    /// If the result of the expression is an integer, it is silently converted into a float.
+    ///
+    /// Fails, if one of the operators in the expression tree fails.
+    pub fn eval_number_with_context(&self, context: &Context) -> Result<FloatType, EvalexprError> {
+        match self.eval_with_context(context) {
+            Ok(Value::Int(int)) => Ok(int as FloatType),
+            Ok(Value::Float(float)) => Ok(float),
+            Ok(value) => Err(EvalexprError::expected_int(value)),
+            Err(error) => Err(error),
+        }
+    }
+
     /// Evaluates the operator tree rooted at this node into a boolean with an the given context.
     ///
     /// Fails, if one of the operators in the expression tree fails.
@@ -137,6 +150,14 @@ impl Node {
         self.eval_int_with_context(&EmptyContext)
     }
 
+    /// Evaluates the operator tree rooted at this node into a float with an empty context.
+    /// If the result of the expression is an integer, it is silently converted into a float.
+    ///
+    /// Fails, if one of the operators in the expression tree fails.
+    pub fn eval_number(&self) -> Result<FloatType, EvalexprError> {
+        self.eval_number_with_context(&EmptyContext)
+    }
+
     /// Evaluates the operator tree rooted at this node into a boolean with an empty context.
     ///
     /// Fails, if one of the operators in the expression tree fails.

tests/integration.rs

@@ -374,6 +374,12 @@ fn test_shortcut_functions() {
             .eval_int_with_context(&context),
         Ok(3)
     );
+    assert_eq!(
+        build_operator_tree("3")
+            .unwrap()
+            .eval_number_with_context(&context),
+        Ok(3.0)
+    );
     assert_eq!(
         build_operator_tree("true").unwrap().eval_boolean(),
         Ok(true)