Re: Typing in Ada

[Marin David Condic <nobody@noplace.com>]

You may be right about structs, but making the argument that because C 
can introduce a new type that it is therefore a strongly typed language 
doesn't seem to follow. Ada won't let you assign a character to an 
integer. C will. While a typedef example may not be 100% equivalent to 
an Ada type, that doesn't cause C to be strongly typed - which was the 
original point.

I'd also observe that just because there is a secret handshake that will 
get C to complain about type compatibility doesn't mean much. Following 
that logic, an assembler program can be made to complain about type 
compatibility (at least at runtime) if you want to do enough work. The 
problem is that typedef doesn't do what one who is acustomed to Ada 
would think it should: "type" - "def" - Define a type.

MDC


Peter C. Chapin wrote:
> 
> I guess my point was that in C typedef does not even attempt to define a 
> new type so comparing it to Ada's 'type' declaration seems unfair. For 
> example if you replace the type declarations in the OP's example with 
> unconstrained subtype declarations, the OP's Ada program compiles with no 
> complaints just like the the example C program using typedef does.
> 
> Now in C there *is* a mechanism for creating new types... it's just that 
> typedef isn't it. Thus it would be more appropriate to compare an Ada 
> program that introduces a new type that is a numeric range to a C program 
> that implements numeric ranges as structs. There is no doubt that the Ada 
> way of creating ranged types is easier and cleaner than any kind of 
> "equivalent" solution in plain C might be. On the other hand, I'm sure C++ 
> could do a much better job of emulating the Ada solution by using 
> templates and overloaded operators.
> 
> In any case, the OP's example didn't seem like a good example of how Ada 
> is more strongly typed than C. It is certainly true that Ada does not do 
> automatic type conversions the way C does, but the OP's example doesn't 
> illustrate that point. In contrast, when I think about a weakly typed 
> language I think about languages like AWK, the shell scripting languages, 
> or perhaps Perl... where the type of a variable shifts around depending on 
> how it is used. For example:
> 
> #!/bin/bash
> COUNT=1
> echo "COUNT is now $COUNT"   # Treat COUNT as a string
> COUNT=$(($COUNT + 1))        # Treat COUNT as a number
> echo "COUNT is now $COUNT"
> 
> Peter


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