[Pharo-dev] Smalltalk = strongly typed

Igor Stasenko siguctua at gmail.com
Fri Aug 2 14:55:53 EDT 2013


I wonder if 'types' can be applied to smalltalk at all.
Saying it is 'unityped' language (since everything is an object) is
same as saying it has no types.

Because where you need types? When you want to manipulate with data,
but in smalltalk all
data manipulation semantics is provided and implemented at primitive
level, but not by the language itself.
At language level the only semantics which is defined is message
passing, closures,
return and assignment.

There is no any rule(s), in smalltalk at language level, saying that
result of expression:

1 + 2

should be of integer type. Because this is provided by implementation
but not defined by language itself e.g.:
it is just a method in corresponding class, which implemented in such
a way that result of expression will be instance of Integer (or
SmallInteger to be precise).
Now, if you change implementation so result will be float (or anything
else), will such change allow you to say, that it is no longer
smalltalk, or that now it is weakly typed or "anything-else typed"?

Because smalltalk code do not operates directly with data, but only
with references to it (which is objects).

Take an assignment, for example.
In staticly-typed language assignment copies the value of expression
to variable, e.g.:

a = 10

"now variable a has value = 10"

in smalltalk, assignment is not copying value, but changing the reference:

a := 10

"now variable a points (or refers) to object '10'"

and thus, whatever 'type' used to represent the integer value 10 is
completely irrelevant
for assignment operation.

-- 
Best regards,
Igor Stasenko.




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