Another update from ingydotnet^djgoku

Task/Null-object/ALGOL-W/null-object.alg

@@ -0,0 +1,10 @@
+begin
+    % declare a record type - will be accessed via references                %
+    record R( integer f1, f2, f3 );
+    % declare a reference to a R instance                                    %
+    reference(R) refR;
+    % assign null to the reference                                           %
+    refR := null;
+    % test for a null reference - will write "refR is null"                  %
+    if refR = null then write( "refR is null" ) else write( "not null" );
+end.

Task/Null-object/Bracmat/null-object.bracmat

@@ -0,0 +1,3 @@
+a:?x*a*?z  {assigns 1 to x and to z}
+a:?x+a+?z  {assigns 0 to x and to z}
+a:?x a ?z  {assigns "" (or (), which is equivalent) to x and to z}

Task/Null-object/Elixir/null-object-1.elixir

@@ -0,0 +1,4 @@
+iex(1)> nil == :nil
+true
+iex(2)> is_nil(nil)
+true

Task/Null-object/Elixir/null-object-2.elixir

@@ -0,0 +1,2 @@
+iex(3)> if nil, do: "not execute"
+nil

Task/Null-object/Ruby/null-object.rb

@@ -5,3 +5,6 @@ puts "$object is nil" if $object.nil?		# global variable, too
 # It recognizes as the local variable even if it isn't executed.
 object = 1  if false
 puts "object is nil" if object.nil?
+
+# nil itself is an object:
+puts nil.class  # => NilClass

Task/Null-object/Rust/null-object.rust

@@ -0,0 +1,20 @@
+// If an option may return null - or nothing - in Rust, it's wrapped
+// in an Optional which may return either the type of object specified
+// in <> or None. We can check this using .is_some() and .is_none() on
+// the Option.
+
+fn check_number(num: &Option<u8>) {
+    if num.is_none() {
+        println!("Number is: None");
+    } else {
+        println!("Number is: {}", num.unwrap());
+    }
+}
+
+fn main() {
+    let mut possible_number: Option<u8> = None;
+    check_number(&possible_number);
+
+    possible_number = Some(31);
+    check_number(&possible_number);
+}