Ring/Lessons/Variables

Variables To create a new variable, you just need to determine the variable name & value. The value will determine the variable type and you can change the value to switch between the types using the same variable name. Syntax: <Variable Name> = <Value> .. tip:: The operator '=' is used here as an Assignment operator and the same operator can be used in conditions, but for testing equality of expressions. .. note:: The Variable will contains the real value (not a reference). This means that once you change the variable value, the old value will be removed from memory (even if the variable contains a list or object). Dynamic Typing Ring is a dynamic programming language that uses `Dynamic Typing <http://en.wikipedia.org/wiki/Type_system>`_. x = "Hello" # x is a string see x + nl x = 5 # x is a number (int) see x + nl x = 1.2 # x is a number (double) see x + nl x = [1,2,3,4] # x is a list see x # print list items x = date() # x is a string contains date see x + nl x = time() # x is a string contains time see x + nl x = true # x is a number (logical value = 1) see x + nl x = false # x is a number (logical value = 0) see x + nl Deep Copy We can use the assignment operator '=' to copy variables. We can do that to copy values like strings & numbers. Also, we can copy complete lists & objects. The assignment operator will do a complete duplication for us. This operation called `Deep Copy <http://en.wikipedia.org/wiki/Object_copy#Deep_copy>`_ list = [1,2,3,"four","five"] list2 = list list = [] See list # print the first list - no items to print See "********" + nl See list2 # print the second list - contains 5 items Weakly Typed Ring is a `weakly typed language <http://en.wikipedia.org/wiki/Strong_and_weak_typing>`_, this means that the language can automatically convert between data types (like string & numbers) when that conversion make sense. Rules: <NUMBER> + <STRING> --> <NUMBER> <STRING> + <NUMBER> --> <STRING> .. note:: The same operator '+' can be used as an arithmetic operator or for string concatenation. Example: x = 10 # x is a number y = "20" # y is a string sum = x + y # sum is a number (y will be converted to a number) Msg = "Sum = " + sum # Msg is a string (sum will be converted to a string) see Msg + nl Ring programming language