Compiler Design

From: John W. Kennedy <jwkenne@xxxxxxxxxxxxx>
Date: Monday, 22 August 2005 12:45

>ANSI PL/I is ex-post-facto, anyway, and allowing declaration after use
>is just plain bad design, not only from the viewpoint of compiler
>writers,

The idea of a language is that it is easy for users to use.
The question is not whether it is easy or otherwise for compiler
writers to write. That's how the computing world got lumbered with C.

> but from the viewpoint of human users,

Use before declaration is appropriate for procedures,
because it permits the user to place them wherever he/she deems
convenient, not where the compiler writer decides.

> and it's one of several
>faults in the design of PL/I occasioned by the notion that everything
>that wasn't a syntax error and that /might/ have an interpretation,
>/should/ have an interpretation.

That wasn't the design philosophy at all.
It was designed to embody the good features of programming
languages of the time, and at the same time to remove the
arbitrary and senseless restrictions that were the bane of
the then versions of FORTRAN and COBOl and Algol.

> It is obvious how that attitude came
>about, considering the many arbitrary restrictions in FORTRAN and
>FORTRAN II --

and Fortran IV

> I felt the same way myself in 1965 -- but it was a bad
>philosophy that led to a number of flaws in the language.

I don't believe so.


.

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