pilgrimk@lafcol.UUCP (Guru Jee) (01/03/89)
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?dmurdoch@watdcsu.waterloo.edu (D.J. Murdoch - Statistics) (01/04/89)
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
david@ms.uky.edu (David Herron -- One of the vertebrae) (01/07/89)
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); If you must do this at runtime, then something like var DummyArr = array[Enum1] of byte ... HowManyEnums = sizeof(DummyArr); ought to work. Another method which requires some attention if you change the declaration of Enum1 would be: const Enum1Max:Enum1 = Four; ... HowManyEnums = ord(Enum1Max) + 1; The best solution would be simply to define a constant with the value you want: const HowManyEnums = 4; TP 5.0 allows expressions to define constants so something like const Enum1Max:Enum1 = Four; HowManyEnums:byte = succ(ord(Enum1Max)); Would also work (though this solution and its runtime counterpart above depend on how TP implements enumerated types, and may break in the future). There may be an even better solution available under 5.0 (I don't have it, myself). Kenneth Herron -- <-- David Herron; an MMDF guy <david@ms.uky.edu> <-- ska: David le casse\*' {rutgers,uunet}!ukma!david, david@UKMA.BITNET <-- Now I know how Zonker felt when he graduated ... <-- Stop! Wait! I didn't mean to!
d87-jse@nada.kth.se (Joakim Sernbrant) (01/11/89)
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? I believe something like sizeof(Enum1) div sizeof(Enum1(ord(One))) will do the trick, but I'm unable to test this right now... -- -- Joakim Sernbrant, Royal Institute of Technology, Stockholm, Sweden -- Internet: d87-jse@nada.kth.se --
mark@hpcllmr.HP.COM (Mark Rozhin) (02/04/89)
>I believe something like sizeof(Enum1) div sizeof(Enum1(ord(One))) will do the >trick, but I'm unable to test this right now... what does sizeof( <constant> ) mean? consider the following: const a = 1; var w : packed record x : 0..1; y : 0..1; z : integer; end; being w.x := a; w.z := a; end somehow, i can only make sense of the size of a constant where the constant is a structure. any thoughts? mr
milne@ics.uci.edu (Alastair Milne) (02/11/89)
In article <950016@hpcllmr.HP.COM> mark@hpcllmr.HP.COM (Mark Rozhin) writes: >>I believe something like sizeof(Enum1) div sizeof(Enum1(ord(One))) will do the >>trick, but I'm unable to test this right now... > >what does sizeof( <constant> ) mean? The same as "sizeof(anything-else)": the amount of memory, typically in bytes, required to store that value; or if the argument is a type, then the amount needed for a value of that type. I'm not quite following the proposed use of "sizeof" here. On the one hand, it looks as if it's being used to measure the ordinality (right term?) of an enumeration -- which it won't do. And the expression "sizeof(Enum1) div sizeof(Enum1(ord(One)))" looks as if it should yield one, since the arguments being passed to "sizeof" are equivalent. I have yet to encounter a way dynamically to determine the number of values in an enumeration, short of having a dialect which provides a MAX function. A fix that's not too hard to use is to have a constant "lastValue" declared as the final value in the enumeration. Besides providing an upper limit for scans, its ordinal is the number of values in the type, less 1. Of course, this takes advantage of TP4/5's relaxed ordering and counting of CONST, TYPE, and VAR sections. If anybody has a better way, I'd be interested to hear. Alastair Milne
abcscnuk@csuna.UUCP (Naoto Kimura) (02/13/89)
In article <7250@paris.ics.uci.edu> Alastair Milne <milne%ics.uci.edu@orion.cf.uci.edu> writes: > ... (text deleted) ... > I have yet to encounter a way dynamically to determine the number of > values in an enumeration, short of having a dialect which provides a > MAX function. PASCAL/VS has functions (really more like a inline macro like sizeof) that returns the maximum and minimum values of a type. They were called something like LoValue() and HiValue(). Another thing that it had a method by which you can get the upper and lower bounds of an array. > ... (text deleted) ... > Alastair Milne //-n-\\ Naoto Kimura _____---=======---_____ (csun!csuna!abcscnuk) ====____\ /.. ..\ /____==== // ---\__O__/--- \\ Enterprise... Surrender or we'll \_\ /_/ send back your *&^$% tribbles !!
scl@virginia.acc.virginia.edu (Steve Losen) (02/15/89)
>In article <7250@paris.ics.uci.edu> Alastair Milne <milne%ics.uci.edu@orion.cf.uci.edu> writes: > ... (text deleted) ... > I have yet to encounter a way dynamically to determine the number of > values in an enumeration, short of having a dialect which provides a > MAX function. Here is a way to do what you want using perfectly legal ISO Standard Pascal (but I'm not saying it's pretty) program prog(output); type enum = (rocky, bullwinckle, boris, natasha, fearless); var junk : array[enum] of integer; i : enum; function maxenum(var array[low..high : enum] of integer) : enum; begin maxenum := high; end; function minenum(var array[low..high : enum] of integer) : enum; begin minenum := low; end; begin for i := minenum(junk) to maxenum(junk) do writeln('nothing up my sleeve'); end. -- Steve Losen scl@virginia.edu University of Virginia Academic Computing Center