On 31.10.2009, at 09:50, Stéphane Rollandin wrote:

>>> If the meaning of #isLiteral is to indicate that what is printed  
>>> can be read back (i.e. will be correctly parsed) then I think it  
>>> is a very useful message that we should keep.
>> #isLiteral mainly indicates which objects can be created at compile  
>> time. They are literally inserted in the compiled method. This must  
>> match the syntax definition of Squeak. There is no question about  
>> not keeping it.
>
> now I'm confused. are all objects anwering true to #isLiteral also  
> have a printed form that can be read back ? should they ?
>
> Stef

It's the other way around - the objects that are recognized  
syntactically in a literal array #(...) must also answer true from  
#isLiteral. See Array>>isLiteral. This of course implies their printed  
form is recognized by the parser.

isSelfEvaluating goes beyond literals - e.g., you cannot put a Point  
into a literal array because of syntactical restrictions, "#(3 at 4)" is  
parsed as "#(3 #@ 4)". But its print string can still be made self- 
evaluating as "{3 at 4}" which is readable. If you want to force a self- 
evaluating expression to be printed you need to use storeString

In older Squeak versions like 3.8 you had this:

{3 at 4} printString
	'#(3 at 4)'

But that is not self-evaluating even if to a novice it might look like  
it was, which is a source of confusion. To avoid that you would need  
this

{3 at 4} storeString
	'((Array new: 1) at: 1 put: 3 at 4; yourself)'

which does evaluate to an object equal to the original one, but looks  
ugly. Now try the same expressions in a more recent Squeak and it's  
much nicer :)

- Bert -