diff --git a/src/main/java/AST.java b/src/main/java/AST.java
index 7ed4bb6..24ce6e4 100644
--- a/src/main/java/AST.java
+++ b/src/main/java/AST.java
@@ -1,2 +1,5 @@
-public abstract class AST {
+import javaslang.render.ToTree;
+
+public abstract class AST implements ToTree<String>{
+    public abstract int maxargs();
 }
diff --git a/src/main/java/AssignStm.java b/src/main/java/AssignStm.java
index d9d1a6e..ba392c5 100644
--- a/src/main/java/AssignStm.java
+++ b/src/main/java/AssignStm.java
@@ -1,3 +1,7 @@
+import javaslang.collection.Tree;
+
+import java.util.Map;
+
 public class AssignStm extends Stm {
 
    public final String id;
@@ -15,4 +19,19 @@ public String toString() {
              ", exp=" + exp +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("AssignStm", Tree.of(id), exp.toTree());
+   }
+
+   @Override
+   public int maxargs() {
+      return exp.maxargs();
+   }
+
+   @Override
+   public void interp(Map<String, Integer> mem) {
+      mem.put(id, exp.eval(mem));
+   }
 }
diff --git a/src/main/java/CompoundStm.java b/src/main/java/CompoundStm.java
index f566e4d..c15352a 100644
--- a/src/main/java/CompoundStm.java
+++ b/src/main/java/CompoundStm.java
@@ -1,3 +1,7 @@
+import javaslang.collection.Tree;
+
+import java.util.Map;
+
 public class CompoundStm extends Stm {
 
    public final Stm stm1;
@@ -15,4 +19,20 @@ public String toString() {
              ", stm2=" + stm2 +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("CompoundStm", stm1.toTree(), stm2.toTree());
+   }
+
+   @Override
+   public int maxargs() {
+      return Math.max(stm1.maxargs(), stm2.maxargs());
+   }
+
+   @Override
+   public void interp(Map<String, Integer> mem) {
+      stm1.interp(mem);
+      stm2.interp(mem);
+   }
 }
diff --git a/src/main/java/EseqExp.java b/src/main/java/EseqExp.java
index a9902cf..7048745 100644
--- a/src/main/java/EseqExp.java
+++ b/src/main/java/EseqExp.java
@@ -1,3 +1,7 @@
+import javaslang.collection.Tree;
+
+import java.util.Map;
+
 public class EseqExp extends Exp {
 
    public final Stm stm;
@@ -15,4 +19,20 @@ public String toString() {
              ", exp=" + exp +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("EseqExp", stm.toTree(), exp.toTree());
+   }
+
+   @Override
+   public int maxargs() {
+      return Math.max(stm.maxargs(), exp.maxargs());
+   }
+
+   @Override
+   public Integer eval(Map<String, Integer> mem) {
+      stm.interp(mem);
+      return exp.eval(mem);
+   }
 }
diff --git a/src/main/java/Exp.java b/src/main/java/Exp.java
index 4dd4145..e1cc0a4 100644
--- a/src/main/java/Exp.java
+++ b/src/main/java/Exp.java
@@ -1,2 +1,6 @@
+import javaslang.collection.Tree;
+import java.util.Map;
+
 public abstract class Exp extends AST {
+    public abstract Integer eval(Map<String, Integer> mem);
 }
diff --git a/src/main/java/IdExp.java b/src/main/java/IdExp.java
index 32ba2df..684b4ad 100644
--- a/src/main/java/IdExp.java
+++ b/src/main/java/IdExp.java
@@ -1,3 +1,7 @@
+import javaslang.collection.Tree;
+
+import java.util.Map;
+
 public class IdExp extends Exp {
    public final String id;
 
@@ -11,4 +15,20 @@ public String toString() {
              "id='" + id + '\'' +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("IdExp " + id);
+   }
+
+   @Override
+   public int maxargs() {
+      return 0;
+   }
+
+   @Override
+   public Integer eval(Map<String, Integer> mem) {
+      Integer x = mem.get(id);
+      return x == null ? 0 : x;
+   }
 }
diff --git a/src/main/java/Main.java b/src/main/java/Main.java
index 24a7a0d..4efb10b 100644
--- a/src/main/java/Main.java
+++ b/src/main/java/Main.java
@@ -1,4 +1,8 @@
 import javaslang.collection.List;
+import javaslang.render.text.Box;
+import javaslang.render.text.Boxes;
+
+import java.util.HashMap;
 
 public class Main {
 
@@ -13,6 +17,12 @@ public static void main(String[] args) {
                               new PrintStm(List.of(new IdExp("x"))));
 
       System.out.println(p);
+      System.out.println(p.toTree().draw());
+      System.out.println(Boxes.box(p.toTree()));
+
+      System.out.printf("maxargs: %d%n", p.maxargs());
 
+      System.out.println("Execução: ");
+      p.interp(new HashMap<String, Integer>());
    }
 }
diff --git a/src/main/java/NumExp.java b/src/main/java/NumExp.java
index 1e070b9..5566d74 100644
--- a/src/main/java/NumExp.java
+++ b/src/main/java/NumExp.java
@@ -1,3 +1,7 @@
+import javaslang.collection.Tree;
+
+import java.util.Map;
+
 public class NumExp extends Exp {
    public final int num;
 
@@ -11,4 +15,20 @@ public String toString() {
              "num=" + num +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("NumExp " + num);
+   }
+
+   @Override
+   public int maxargs() {
+      return 0;
+   }
+
+    @Override
+    public Integer eval(Map<String, Integer> mem) {
+       return num;
+    }
 }
+
diff --git a/src/main/java/OpExp.java b/src/main/java/OpExp.java
index a25cf35..5e27b60 100644
--- a/src/main/java/OpExp.java
+++ b/src/main/java/OpExp.java
@@ -1,3 +1,7 @@
+import javaslang.collection.Tree;
+
+import java.util.Map;
+
 public class OpExp extends Exp {
 
    public enum Op { PLUS, MINUS, TIMES, DIV }
@@ -20,4 +24,29 @@ public String toString() {
              ", op=" + op +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("OpExp " + op, left.toTree(), right.toTree());
+   }
+
+   @Override
+   public int maxargs() {
+      return Math.max(left.maxargs(), right.maxargs());
+   }
+
+   @Override
+   public Integer eval(Map<String, Integer> mem) {
+      Integer x = left.eval(mem);
+      Integer y = right.eval(mem);
+
+      switch (op){
+         case PLUS: return x + y;
+         case MINUS: return x - y;
+         case TIMES: return x * y;
+         case DIV: return  x/y;
+         default: return 0;
+
+      }
+   }
 }
diff --git a/src/main/java/PrintStm.java b/src/main/java/PrintStm.java
index ba730ef..fc7f869 100644
--- a/src/main/java/PrintStm.java
+++ b/src/main/java/PrintStm.java
@@ -1,4 +1,8 @@
 import javaslang.collection.List;
+import javaslang.collection.Tree;
+import javaslang.render.ToTree;
+
+import java.util.Map;
 
 public class PrintStm extends Stm {
 
@@ -14,4 +18,25 @@ public String toString() {
              "exps=" + exps +
              '}';
    }
+
+   @Override
+   public Tree.Node<String> toTree() {
+      return Tree.of("PrintStm", exps.map(Exp::toTree));
+   }
+
+   @Override
+   public int maxargs() {
+       int aux = exps.length();
+
+       for(Exp e : exps)
+           aux = Math.max(e.maxargs(), aux);
+
+       return exps.length();
+   }
+
+    @Override
+    public void interp(Map<String, Integer> mem) {
+        exps.forEach(e -> System.out.println(e.eval(mem) + " "));
+        System.out.println();
+    }
 }
diff --git a/src/main/java/Stm.java b/src/main/java/Stm.java
index d406e8b..288a2b5 100644
--- a/src/main/java/Stm.java
+++ b/src/main/java/Stm.java
@@ -1,2 +1,6 @@
+import java.util.Map;
+
 public abstract class Stm extends AST {
+    public abstract void interp(Map<String, Integer> mem);
+
 }
diff --git a/straightline.iml b/straightline.iml
new file mode 100644
index 0000000..993e87b
--- /dev/null
+++ b/straightline.iml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_8">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="Maven: org.apache.commons:commons-lang3:3.5" level="project" />
+    <orderEntry type="library" name="Maven: io.javaslang:javaslang:2.0.6" level="project" />
+    <orderEntry type="library" name="Maven: io.javaslang:javaslang-match:2.0.6" level="project" />
+    <orderEntry type="library" name="Maven: io.javaslang:javaslang-render:2.0.0" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.12" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.assertj:assertj-core:3.7.0" level="project" />
+  </component>
+</module>
\ No newline at end of file