Path: utzoo!utgpu!watmath!watdcsu!dmurdoch
From: dmurdoch@watdcsu.waterloo.edu (D.J. Murdoch - Statistics)
Newsgroups: comp.lang.pascal
Subject: Re: Enumerated types in TP40
Keywords: none
Message-ID: <5390@watdcsu.waterloo.edu>
Date: 4 Jan 89 14:39:50 GMT
References: <363@lafcol.UUCP>
Reply-To: dmurdoch@watdcsu.waterloo.edu (D.J. Murdoch - Statistics)
Organization: U. of Waterloo, Ontario
Lines: 31

In article <363@lafcol.UUCP> pilgrimk@lafcol.UUCP (Guru Jee) writes:
>How can the number of elements in an enumerated type be determined?
>
> e.g. type
>          Enum1 = (One, Two, Three, Four);
>          Enum2 = (_One, _Two, _Three);
>
>I would like to get a value of 4 for the no. of elements in any 
>variable declared as "Enum1" and 3 for those declared as "Enum2". Is
>this possible?

Not easily - TP doesn't give any min and max functions that work on variables,
let alone types.  However, if you are really desperate, it can be done, sort
of.  If you enable range checking, then assigning a byte with value 4 to a
variable of type Enum1 will cause an error.  So, one way to count an enumerated
type is to see how far you get in assigning values starting with 0 to it.
 
There's a faster but even worse way to do it, however.  The way range checking
works in TP4 (I'm not sure about any other version) is to store the upper and 
lower limits as longints somewhere in the code segment, and pass the address
of these limits, along with the value to be checked, to a little subroutine
in the system unit.  I once wrote an inline routine that could look back through
the code until it found the pointer to the limits, and returned that.   Then
you could find out (and even change) the limits that the range checker was 
using.  I was applying this to checking the limits on the subscripts of an
array, but I imagine the same idea would work to find the limits on any type.

After I wrote it, I couldn't find any situation where I was desperate enough
to want to use it, and I've lost it now.

Duncan Murdoch