🚀 go-pugleaf

In article <3162FD33.61F7@uh.edu> Jeff M Younker <jeff@uh.edu> writes:

> Value types are really cool from a conceptual point of view, but
> I am not so sure that they are necessary to achieve fast numerical
> code.  If my understanding is correct, Fortran 77 (the premiere
> language of high speed code) treats integers, floats and complex
> numbers as references.  I have yet to hear anyone complain about
> the speed of Fortran code.

Yes and no.  In Fortran 77, all objects are what C calls "automatic"
or "static" [*], and what Eiffel calls "expanded".  That is, if x and
y are of type REAL*8, then the expression x = y assigns the value of y
to x.  Variables are allocated on the stack or in static storage,
rather than being dynamically allocated, and you're manipulating
values rather than not pointers.  In other words, all Fortran 77
objects are value types.

What is true is that parameters in Fortran 77 subroutines are passed
by reference rather than by value: you can, for example, modify the
values of the arguments you're passed.  Fortran 77 imposes very strong
constraints, though (such as no aliasing or recursion), so the
semantics of Fortran subroutine calls really doesn't have much in
common with an all-pointer language like Java or Smalltalk.

---------------------------

[*] One interesting bit of trivia: a lot of people, including a lot of
Fortran programmers, think that the Fortran 77 standard guarantees
that variables are static.  That's false; it just happens that many
implementations do that, and many programmers have written incorrect
code that relies on such behavior.
-- 
Matt Austern
SGI: MTI Compilers Group
austern@isolde.mti.sgi.com