Let's say I have an array I need to store string values as well as double values. I know I can store the doubles as strings, and just deal with the conversions, but is it possible to use an array with two data types?
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How much performance is important? If it is, I could have tried writing a custom class storing them separately but exposing them as one.Aliostad– Aliostad2010-09-07 19:41:12 +00:00Commented Sep 7, 2010 at 19:41
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how do you detect whether it's a double or string you pull out. Are they always in the same order or?Rune FS– Rune FS2010-09-07 19:46:47 +00:00Commented Sep 7, 2010 at 19:46
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4 Answers
You may use object[] and do some type checking. You will get some boxing/unboxing when accessing the doubles, but that will be faster than double.Parse() anyway.
An alternative is to create a class with both types and a marker:
class StringOrDouble
{
private double d;
private string s;
private bool isString;
StringOrDouble(double d)
{
this.d = d;
isString = false;
}
StringOrDouble(string s)
{
this.s = s;
isString = true;
}
double D
{
get
{
if (isString)
throw new InvalidOperationException("this is a string");
return d;
}
}
string S
{
get
{
if (!isString)
throw new InvalidOperationException("this is a double");
return s;
}
}
bool IsString { get { return isString; } }
}
and then create an array of StringOrDouble. This will save you from some typechecking and boxing, but will have a larger memory overhead.
1 Comment
sooprise
^ is what you are describing here a structure?
sure use:
object[], ArrayList, or List<Object>;
You'll have to cast, and probably pay a boxing penalty for the doubles, but they will allow you to store two different types.
5 Comments
sooprise
Which would you recommend for maximum efficiency? I'm dealing with 50k element sized arays.
Justin Niessner
@Soo - Is it always 50k elements and is each of the 50k elements always filled?
Richard J. Ross III
I would think, that if you are needing to resize the array, that the arraylist or List<Object> would be better. If there is no resizing necessary, then just use an object[], as that will be better for fast lookup than the List<Object> or ArrayList.
kemiller2002
50k...The three pretty much do the same thing, in terms of storage, but honestly, I would probably reconsider using an array at all and try and use several smaller structures.
KeithS
Array is generally fastest, since it doesn't have the variable-length overhead of ArrayList and List.
Not the most efficient usage, but how about for flexibility:
var a = new object[] {1,2,3,"paul",5.5}
or even
var a = new object[] {1,2,3,"paul",5.5, new List<string>() {"apple","banana","pear"} }
Comments
object[] and ArrayList are two decent options; it depends on whether you need a traditional fixed-length array or a vector (variable-length array). Further, I would "wrap" one of these in a custom class that did some type-checking, if strings and doubles are the ONLY things you can deal with, and you need to be able to get them back out as strings and doubles.
