diff --git a/desktop/sources/scripts/library.js b/desktop/sources/scripts/library.js
index a685542..532dc89 100644
--- a/desktop/sources/scripts/library.js
+++ b/desktop/sources/scripts/library.js
@@ -66,6 +66,10 @@ function Library (ronin) {
     return arr.map(fn)
   }
 
+  this.filter = (fn, arr) => {
+    return arr.filter(fn)
+  }
+
   this.first = (arr) => {
     return arr[0]
   }
@@ -155,7 +159,12 @@ function Library (ronin) {
   this.mul = function (a, b) {
     return a * b
   }
+
   this.div = function (a, b) {
     return a / b
   }
+
+  this.mod = function (a, b) {
+    return a % b
+  }
 }
diff --git a/desktop/sources/scripts/lisp.js b/desktop/sources/scripts/lisp.js
index c54763e..31ea659 100644
--- a/desktop/sources/scripts/lisp.js
+++ b/desktop/sources/scripts/lisp.js
@@ -35,6 +35,13 @@ function Lisp (input, lib) {
 
         return interpret(input[2], new Context(lambdaScope, context))
       }
+    },
+
+    if: function (input, context) {
+      if (interpret(input[1], context)) {
+        return interpret(input[2], context)
+      }
+      return interpret(input[3], context)
     }
   }
 
diff --git a/examples/arrays.lisp b/examples/arrays.lisp
index 76306e6..3389fa1 100644
--- a/examples/arrays.lisp
+++ b/examples/arrays.lisp
@@ -5,6 +5,12 @@
   (print (rest (1 2 3)))
 )
 
+(print 
+  (filter 
+    (lambda (a) (eq 0 (mod a 2))) 
+    (1 2 3 4 5))
+)
+
 (
   (clear) 
   (map (lambda (a)
diff --git a/examples/logic.lisp b/examples/logic.lisp
index f45f176..2c612d9 100644
--- a/examples/logic.lisp
+++ b/examples/logic.lisp
@@ -6,4 +6,6 @@
   (print (and 1 false 2))
 
   (print (or false false 2 false))
+
+  (if (gt 1 2) (print "ok") (print "not ok"))
 )
\ No newline at end of file