diff --git a/src/interface/mod.rs b/src/interface/mod.rs
index 2e59209..fe1b073 100644
--- a/src/interface/mod.rs
+++ b/src/interface/mod.rs
@@ -1,8 +1,7 @@
-use crate::token;
+use crate::{token, HashMapContext};
 use crate::tree;
 use crate::value::TupleType;
 use crate::Context;
-use crate::EmptyContext;
 use crate::EmptyType;
 use crate::EvalexprError;
 use crate::EvalexprResult;
@@ -24,7 +23,7 @@ use crate::EMPTY_VALUE;
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval(string: &str) -> EvalexprResult<Value> {
-    eval_with_context(string, &EmptyContext)
+    eval_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string with the given context.
@@ -97,21 +96,21 @@ pub fn build_operator_tree(string: &str) -> EvalexprResult<Node> {
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_string(string: &str) -> EvalexprResult<String> {
-    eval_string_with_context(string, &EmptyContext)
+    eval_string_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into an integer.
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_int(string: &str) -> EvalexprResult<IntType> {
-    eval_int_with_context(string, &EmptyContext)
+    eval_int_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into a float.
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_float(string: &str) -> EvalexprResult<FloatType> {
-    eval_float_with_context(string, &EmptyContext)
+    eval_float_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into a float.
@@ -119,28 +118,28 @@ pub fn eval_float(string: &str) -> EvalexprResult<FloatType> {
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_number(string: &str) -> EvalexprResult<FloatType> {
-    eval_number_with_context(string, &EmptyContext)
+    eval_number_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into a boolean.
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_boolean(string: &str) -> EvalexprResult<bool> {
-    eval_boolean_with_context(string, &EmptyContext)
+    eval_boolean_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into a tuple.
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_tuple(string: &str) -> EvalexprResult<TupleType> {
-    eval_tuple_with_context(string, &EmptyContext)
+    eval_tuple_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into an empty value.
 ///
 /// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
 pub fn eval_empty(string: &str) -> EvalexprResult<EmptyType> {
-    eval_empty_with_context(string, &EmptyContext)
+    eval_empty_with_context_mut(string, &mut HashMapContext::new())
 }
 
 /// Evaluate the given expression string into a string with the given context.
diff --git a/tests/integration.rs b/tests/integration.rs
index 5d7012b..2e6d719 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -2,9 +2,6 @@ extern crate evalexpr;
 
 use evalexpr::{error::*, *};
 
-#[cfg(feature = "serde")]
-mod serde;
-
 #[test]
 fn test_unary_examples() {
     assert_eq!(eval("3"), Ok(Value::Int(3)));
@@ -639,3 +636,15 @@ fn test_tuple_definitions() {
         Ok(vec![Value::from(1), Value::from(2)])
     );
 }
+
+#[test]
+fn test_implicit_context() {
+    assert_eq!(eval("a = 2 + 4 * 2; b = -5 + 3 * 5; a == b"), Ok(Value::from(true)));
+    assert_eq!(eval_boolean("a = 2 + 4 * 2; b = -5 + 3 * 5; a == b"), Ok(true));
+    assert_eq!(eval_int("a = 2 + 4 * 2; b = -5 + 3 * 5; a - b"), Ok(0));
+    assert_eq!(eval_float("a = 2 + 4 * 2; b = -5 + 3 * 5; a - b + 0.5"), Ok(0.5));
+    assert_eq!(eval_number("a = 2 + 4 * 2; b = -5 + 3 * 5; a - b"), Ok(0.0));
+    assert_eq!(eval_empty("a = 2 + 4 * 2; b = -5 + 3 * 5;"), Ok(()));
+    assert_eq!(eval_tuple("a = 2 + 4 * 2; b = -5 + 3 * 5; a, b + 0.5"), Ok(vec![Value::from(10), Value::from(10.5)]));
+    assert_eq!(eval_string("a = \"xyz\"; b = \"abc\"; c = a + b; c"), Ok("xyzabc".to_string()));
+}
\ No newline at end of file
diff --git a/tests/serde.rs b/tests/serde.rs
index bb261d1..77af185 100644
--- a/tests/serde.rs
+++ b/tests/serde.rs
@@ -1,3 +1,5 @@
+#![cfg(feature = "serde")]
+
 use evalexpr::{build_operator_tree, Node};
 
 #[test]