What is Expressiveness in a Computer Language

[Matthias Blume]

"Rob Thorpe" <robert.thorpe at antenova.com> writes:

> Matthias Blume wrote:
>> "Rob Thorpe" <robert.thorpe at antenova.com> writes:
>>
>> > I think we're discussing this at cross-purposes.  In a language like C
>> > or another statically typed language there is no information passed
>> > with values indicating their type.
>>
>> You seem to be confusing "does not have a type" with "no type
>> information is passed at runtime".
>>
>> > Have a look in a C compiler if you don't believe me.
>>
>> Believe me, I have.
>
> In a C compiler the compiler has no idea what the values are in the
> program.

It is no different from any other compiler, really.  If the compiler
sees the literal 1 in a context that demands type int, then it knows
perfectly well what value that is.

> It knows only their type in that it knows the type of the variable they
> are contained within.
> Would you agree with that?
>
>> > No it doesn't. Casting reinterprets a value of one type as a value of
>> > another type.
>> > There is a difference.  If I cast an unsigned integer 2000000000 to a
>> > signed integer in C on the machine I'm using then the result I will get
>> > will not make any sense.
>>
>> Which result are you getting?  What does it mean to "make sense"?
>
> Well the right one actually, bad example.
>
> But, if I cast an unsigned int 2500000000 to signed I get -1794967296.

So, why do you think this "does not make sense"?  And, as this example
illustrates, casting in C maps values to values.  Depending on the
types of the source and the target, a cast might change the underlying
representation, or it might leave it the same.  But it does produce a
value, and the result value is usually not the same as the argument
value, even if the representation is the same.

Matthias