[Bluej-discuss] confusion over =

[Michael Kölling]

On 30 Nov 2007, at 11:22, Michael E. Caspersen wrote:

> ... teaching language Blue...

Yes, in Blue everything was an object. And operations had a uniform  
syntax, for example

    2.add(4)

But then there were "aliases". I have just looked at the language spec  
again (after a long time!). Here is what it says:

"All types in Blue are classes and all data are objects.  This general  
rule
simplifies the language design.  There are, however, a number of data  
types
for which it is convenient to use syntax other than the Blue object  
call to
perform one of their operations.  The reason for this can be:

	• Another syntax is commonly used and is therefore more intuitive (e.g.
	  3 + 5 for integer addition, rather than 3.add (5)  ).
	• Another syntax simplifies use of elementary constructs which should  
be
	  used by beginners before the underlying language concepts need to be
	  understood, e.g.
		print (“result=“, 42)
	   instead of
		output.write (“result=“.concat (42.toString))
	• Another syntax is more convenient (usually because it is shorter, see
	  above).

For these reasons, several operations on the predefined classes are  
supported
by special syntax.  This special syntax is allowed in addition to the  
standard
object-call syntax generally available for all classes, and is  
referred to as
aliases.
...
Note that aliases are a pure syntactic addition which does not add any
functionality to the language.  They do not affect the semantics or the
theoretical language description of Blue (although they are part of the
language), and are purely intended to increase readability and  
intuitivity of
statements. "

Oh yes, and Blue uses, of course, = for equality check and := for  
assignment...  :)

If anyone is really interested in dead old languages, the spec is here:

	http://www.cs.kent.ac.uk/people/staff/mik/blue/doc/spec-102.pdf

Michael