[comp.lang.modula2] Exceptions & single output

wick%instr.camosun.bcc.cdn%ubc.CSNET@RELAY.CS.NET.UUCP (02/10/87)

>        Correct me if I am wrong but from my observations of Modula-2, I
> think the reason why explicit exception handling mechanisms do not exist
> is mainly because it was designed under the auspice of "Structured
> Programming".  This consists mechanisms such as iteration, sequence and
> decision but also includes recommendations on functionality such as
> "Single input, single output" 

Then why did he include multiple RETURN's for function procedures
and  why did he include multiple EXIT's from LOOP's????

CASHEN.SBDERX@XEROX.COM.UUCP (02/11/87)

REF:
Then why did he include multiple RETURN's for function procedures
and  why did he include multiple EXIT's from LOOP's????

My (Exceptional) opinion is:

Designing a programming language is in some respects a compromise on the
ideal. According to my knowledge of "Structured Programming" (zero or
otherwise?) one of the requirements or ideals is to provide fundamental
function definitions. This I believe to mean that, if one uses something
like a "Top Down" design methodology then the ultimate goal is to
produce a Procedure or Function declaration which performs only one
unique function. This Procedure or Function would have one entry point
(Procedure Call) and one exit point (Return). In my coding experience
(yes I do have some) I have defined single Procedures to perform more
than one function and also introduced multiple exit points in the guise
of expedience but in the strictest sense, that is not structured
programming. I can only guess that such facilities are included in
(structured?) languages like Modula-2 to enhance the armoury of the
programmer. As to why exception handlers were not also included I can
only presume it is because of flow control considerations (go from
whence you came...) etc.
    Even so I can only offer my opinion and I don't want to be the one,
to state what was in the mind of Ravel or Monet when they produced their
greatest pieces. As a viewer I can only offer my impression. Short of
asking the famed Mr.W. why he did or did not include Exception handlers
I think we are stuck....
    In the mean time, please refer all Exocets and IBM's to chiefly
myself for future digestion. 
     
    Mike.