BOTCHAIR@UOGUELPH.BITNET (Alex Bewley) (09/30/89)
I was struck with an urge to think just the other day and came up with the
following observation. I was flipping through some Ada books in the library
('cause they outnumber Modula-2 books about 20 to 1) and Ada seems to have a
feature where you can define an operator for non-standard types. For example
suppose you want to add two complex numbers. You have to:
Result := AddComplex(A, B);
Which detracts from structure readability (say what?). Well, what I mean
is that, for example, when adding CARDINALs you just have:
Result := A + B;
Which (algebraically) reads exactly as you mean it. In Ada you can
define the '+' operator to be able to handle the Complex number type.
Would such a feature be warranted in Modula-2?
Here is some theoretical code:
(* necessary IMPORTs *)
TYPE
Complex; (* abstract type *)
OPERATORTYPE
"+" : AddComplex(Complex, Complex) : Complex; (* procedures called *)
"-" : SubComplex(Complex, Complex) : Complex; (* when operators used *)
":=" : DefineComplex(REAL, REAL) : Complex;
VAR
Result : Complex;
A, B : Complex;
BEGIN
A := 2.0, 2.0;
B := 4.0, 4.0;
Result := A + B;
END;
The compiler or translator could substitute the necessary procedure
and make sure that the correct types are being used.
Thus, the compilable code would look like:
BEGIN
A := DefineComplex(2.0, 2.0);
B := DefineComplex(4.0, 4.0);
Result := AddComplex(A, B);
END;
This kind of operator definability could be used to simplify reading
of bit shifting operations. For example:
EquipList := (BIOSResult SHL 5) XOR OtherBIOSResult;
Rather than:
EquipList := Shl(BIOSResult, 5);
EquipList := Xor(EquipList, OtherBIOSResult);
Something to think on...
Alex
Just this guy...sludwig@ics.uci.edu (Stefan Ludwig) (09/30/89)
In article <INFO-M2%89093000360807@UCF1VM> Modula2 List <INFO-M2%UCF1VM.BITNET@PSUVM.PSU.EDU> writes: [stuff deleted] > Which (algebraically) reads exactly as you mean it. In Ada you can > define the '+' operator to be able to handle the Complex number type. > > Would such a feature be warranted in Modula-2? > > Here is some theoretical code: [stuff deleted] > The compiler or translator could substitute the necessary procedure > and make sure that the correct types are being used. > Thus, the compilable code would look like: [stuff deleted] I recently suggested operator overloading to Prof. Wirth. His argument is: the possibility you gain for coding programs does not justify the added complexity to the compiler. This guy is running for 'the smallest compiler in the world'-contest. His compilers are *really* small and *fast*. The Oberon compiler for the Ceres (NS32000 based) is just 39KB object code! It sure would be a nice feature to have, especially when you have object- oriented features (like in Object-Oberon). We're thinking about adding that to our Object-Oberon compiler...We'll see, just stay tuned. > > Alex > Just this guy... Stefan Stefan HM Ludwig "Don't flame my english, it's what they teach us in Swiss schools" E-MAIL: sludwig@ics.uci.edu until October 21st ludwig@badile.iis.ethz.ch later
pepers@cpsc.ucalgary.ca (Bradley Pepers) (10/01/89)
Oberon sounds really interesting. I missed anything talking in detail about it so where can I find information on it? And also on Object-Oberon. Brad Pepers
toma@tekgvs.LABS.TEK.COM (Tom Almy) (10/02/89)
In article <1989Sep30.050044.12442@paris.ics.uci.edu> Stefan Ludwig <sludwig@ics.uci.edu> writes: >This guy [Wirth] is running for 'the smallest compiler >in the world'-contest. His compilers are *really* small and *fast*. >The Oberon compiler for the Ceres (NS32000 based) is just 39KB object code! Well he should give up on winning the Smallest Compiler contest and instead go for the "Most Useful Language" contest. He'll never win smallest compiler since typical Forth language compilers are about 1k byte. As long as the compiler fits on *my* machine *I* don't care how big or small it is as long as it saves me programming/debugging time! Tom Almy toma@tekgvs.labs.tek.com Standard Disclaimers Apply
treese@crltrx.crl.dec.com (Win Treese) (10/06/89)
In article <INFO-M2%89093000360807@UCF1VM> Modula2 List <INFO-M2%UCF1VM.BITNET@PSUVM.PSU.EDU> writes: > > I was struck with an urge to think just the other day and came up with the > following observation. I was flipping through some Ada books in the library > ('cause they outnumber Modula-2 books about 20 to 1) and Ada seems to have a > feature where you can define an operator for non-standard types. For example > suppose you want to add two complex numbers. You have to: It's worth noting that CLU does this (and has been around for a long time). The compiler can do it automatically: a + b is simply syntactic sugar for typeof(a)$add(a, b) The types of a and b must match, of course. 3 + 5 is just int$add(3, 5). Win Treese Cambridge Research Lab treese@crl.dec.com Digital Equipment Corp.