diff --git a/doc/examples/use-case-1.txt b/doc/examples/use-case-1.b
similarity index 80%
rename from doc/examples/use-case-1.txt
rename to doc/examples/use-case-1.b
index edf5d7a..e298cf0 100644
--- a/doc/examples/use-case-1.txt
+++ b/doc/examples/use-case-1.b
@@ -1,5 +1,5 @@
 fun h = 3*x;
-function g = { x - 2: x < 3, 
+function g = { x - 2: x < 3,
                x^3: x >= 5,
                x: x > 7
              };
diff --git a/doc/examples/use-case-10.txt b/doc/examples/use-case-10.b
similarity index 100%
rename from doc/examples/use-case-10.txt
rename to doc/examples/use-case-10.b
diff --git a/doc/examples/use-case-11.txt b/doc/examples/use-case-11.b
similarity index 100%
rename from doc/examples/use-case-11.txt
rename to doc/examples/use-case-11.b
diff --git a/doc/examples/use-case-12.txt b/doc/examples/use-case-12.b
similarity index 100%
rename from doc/examples/use-case-12.txt
rename to doc/examples/use-case-12.b
diff --git a/doc/examples/use-case-13.b b/doc/examples/use-case-13.b
new file mode 100644
index 0000000..a7f5f7f
--- /dev/null
+++ b/doc/examples/use-case-13.b
@@ -0,0 +1,3 @@
+if ("Hola" + g == 2) {
+    print("Funciona");
+}
\ No newline at end of file
diff --git a/doc/examples/use-case-13.txt b/doc/examples/use-case-13.txt
deleted file mode 100644
index 598e31d..0000000
--- a/doc/examples/use-case-13.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-if ("Hola" + g == 2) {
-	print("Funciona");
-}
\ No newline at end of file
diff --git a/doc/examples/use-case-14.txt b/doc/examples/use-case-14.b
similarity index 100%
rename from doc/examples/use-case-14.txt
rename to doc/examples/use-case-14.b
diff --git a/doc/examples/use-case-15.b b/doc/examples/use-case-15.b
new file mode 100644
index 0000000..80237e9
--- /dev/null
+++ b/doc/examples/use-case-15.b
@@ -0,0 +1,4 @@
+if (1 == 1) {
+    print("Hola");
+}
+}
\ No newline at end of file
diff --git a/doc/examples/use-case-15.txt b/doc/examples/use-case-15.txt
deleted file mode 100644
index c0d826e..0000000
--- a/doc/examples/use-case-15.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-if (1 == 1) {
-	print("Hola");
-}
-}
\ No newline at end of file
diff --git a/doc/examples/use-case-2.txt b/doc/examples/use-case-2.b
similarity index 53%
rename from doc/examples/use-case-2.txt
rename to doc/examples/use-case-2.b
index c00d574..56049e2 100644
--- a/doc/examples/use-case-2.txt
+++ b/doc/examples/use-case-2.b
@@ -1,4 +1,4 @@
-function g = { x - 2: x < 3, 
+function g = { x - 2: x < 3,
                x^3: x >= 5,
                x: x > 7
              };
diff --git a/doc/examples/use-case-3.txt b/doc/examples/use-case-3.b
similarity index 100%
rename from doc/examples/use-case-3.txt
rename to doc/examples/use-case-3.b
diff --git a/doc/examples/use-case-4.txt b/doc/examples/use-case-4.b
similarity index 100%
rename from doc/examples/use-case-4.txt
rename to doc/examples/use-case-4.b
diff --git a/doc/examples/use-case-5.txt b/doc/examples/use-case-5.b
similarity index 100%
rename from doc/examples/use-case-5.txt
rename to doc/examples/use-case-5.b
diff --git a/doc/examples/use-case-6.txt b/doc/examples/use-case-6.b
similarity index 100%
rename from doc/examples/use-case-6.txt
rename to doc/examples/use-case-6.b
diff --git a/doc/examples/use-case-7.txt b/doc/examples/use-case-7.b
similarity index 100%
rename from doc/examples/use-case-7.txt
rename to doc/examples/use-case-7.b
diff --git a/doc/examples/use-case-8.txt b/doc/examples/use-case-8.b
similarity index 54%
rename from doc/examples/use-case-8.txt
rename to doc/examples/use-case-8.b
index ee36fd6..5d79582 100644
--- a/doc/examples/use-case-8.txt
+++ b/doc/examples/use-case-8.b
@@ -1,2 +1,3 @@
 fun f = f(3) * x * 4 + 3;
-fun g =  f(3) + f'(3)*(x-3) + f''(3)/2 * (x-3)^2 + f'''(3) / 6 * (x-3)^3 + f''''(3) / 24 * (x-3)^4;
\ No newline at end of file
+fun g =  f(3) + f'(3)*(x-3) + f''(3)/2 * (x-3)^2 + f'''(3) / 6 * (x-3)^3 + f''''(3) / 24 * (x-3)^4;
+fun g =  f(2) + integrate(derivative())
\ No newline at end of file
diff --git a/doc/examples/use-case-9.txt b/doc/examples/use-case-9.b
similarity index 100%
rename from doc/examples/use-case-9.txt
rename to doc/examples/use-case-9.b