Improve map type functionality

src/context/mod.rs

@@ -4,7 +4,7 @@
 //! This crate implements two basic variants, the `EmptyContext`, that returns `None` for each identifier and cannot be manipulated, and the `HashMapContext`, that stores its mappings in hash maps.
 //! The HashMapContext is type-safe and returns an error if the user tries to assign a value of a different type than before to an identifier.
 
-use std::collections::BTreeMap;
+use std::{collections::BTreeMap, fmt::Display};
 
 use crate::{
     function::Function,
@@ -46,6 +46,18 @@ pub struct VariableMap {
     variables: BTreeMap<String, Value>,
 }
 
+impl Display for VariableMap {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "(")?;
+
+        for (key, value) in &self.variables {
+            write!(f, " {} = {};", key, value)?;
+        }
+
+        write!(f, " )")
+    }
+}
+
 impl PartialEq for VariableMap {
     fn eq(&self, other: &Self) -> bool {
         if self.variables.len() != other.variables.len() {
@@ -85,30 +97,37 @@ impl Context for VariableMap {
 
 impl ContextWithMutableVariables for VariableMap {
     fn set_value(&mut self, identifier: &str, value: Value) -> EvalexprResult<()> {
-        println!("{:#?}", self);
-        println!("{}", identifier);
-
         let split = identifier.split_once(".");
+
         if let Some((map_name, next_identifier)) = split {
             if let Some(map_value) = self.variables.get_mut(map_name) {
                 if let Value::Map(map) = map_value {
-                    map.set_value(next_identifier, value)?;
+                    map.set_value(next_identifier, value)
                 } else {
                     return Err(EvalexprError::ExpectedMap {
                         actual: map_value.clone(),
                     });
                 }
             } else {
-                let mut new_map = BTreeMap::new();
-                new_map.insert(next_identifier.to_string(), value);
-                let map_var = Value::Map(VariableMap { variables: new_map });
-                self.variables.insert(map_name.to_string(), map_var);
+                let mut new_map = VariableMap {
+                    variables: BTreeMap::new(),
+                };
+
+                new_map.set_value(next_identifier, value)?;
+                self.variables
+                    .insert(map_name.to_string(), Value::Map(new_map));
+
+                Ok(())
             }
+        } else if self.variables.contains_key(identifier) {
+            Err(EvalexprError::ExpectedMap {
+                actual: value.clone(),
+            })
         } else {
             self.variables.insert(identifier.to_string(), value);
-        }
 
-        Ok(())
+            Ok(())
+        }
     }
 }
 

src/value/display.rs

@@ -23,7 +23,7 @@ impl Display for Value {
                 write!(f, ")")
             },
             Value::Empty => write!(f, "()"),
-            Value::Map(_) => write!(f, "{:?}", self),
+            Value::Map(map) => write!(f, "{}", map),
         }
     }
 }