feat(eval): provide evaluation of expression statements and integer l…

…iterals

eval/eval.go

@@ -0,0 +1,28 @@
+package eval
+
+import (
+    "monkey/ast"
+    "monkey/object"
+)
+
+func Eval(node ast.Node) object.Object {
+    switch node := node.(type) {
+    case *ast.Program:
+        return evalStatements(node.Statements)
+    case *ast.ExpressionStatement:
+        return Eval(node.Expression)
+    case *ast.IntegerLiteral:
+        return &object.Integer{Value: node.Value}
+    }
+
+    return nil
+}
+
+func evalStatements(stmts []ast.Statement) object.Object {
+    var result object.Object
+
+    for _, stmt := range stmts {
+        result = Eval(stmt)
+    }
+    return result
+}