foreach insted of for

14y1.6kVisual Basic .NET

I wish to whether it is possible to modify this program by using foreach instead for loop

using System;
public class ParallelArrays
{
public static void Main()
{
int[] validValues = { 101, 108, 201, 213, 266, 304, 311, 409, 411, 412 };

double[] prices = { 0.89, 1.23, 3.50, 0.69, 5.79, 3.19, 0.99, 0.89, 1.26, 8.00 };

//parallel array

int itemOrdered = 311;

for (int i = 0; i < validValues.Length; ++i)
{
if (itemOrdered == validValues[i]) //order doesn't matter
{
Console.WriteLine(prices[i]);
}
}
Console.ReadKey();
}
}
/*
0.99
*/

4 Replies

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Vulpes14y ago
If you're using .NET 4.0, then the new Tuple class is a good way to represent parallel arrays. In fact you can easily represent up to 8 such arrays.

Here's the two array case using tuples:

using System;

public class ParallelArrays
{
public static void Main()
{
int[] validValues = { 101, 108, 201, 213, 266, 304, 311, 409, 411, 412 };

double[] prices = { 0.89, 1.23, 3.50, 0.69, 5.79, 3.19, 0.99, 0.89, 1.26, 8.00 };

Tuple[] tuples = new Tuple[validValues.Length];

for(int i = 0; i < validValues.Length; i++)
{
tuples[i] = Tuple.Create(validValues[i], prices[i]);
}

//parallel array using tuples

int itemOrdered = 311;

foreach (Tuple tuple in tuples)
{
if (itemOrdered == tuple.Item1) //order doesn't matter
{
Console.WriteLine(tuple.Item2);
}
}
Console.ReadKey();
}
}

You can also create a custom class which has the merit that you can use sensible names (not just Item1, Item2) for the parallel elements. However, if you're not too bothered about that, then tuples are more convenient.
Sam Hobbs14y ago
Of course there are other possibilities that do not use either for or foreach.

If the data exists in the manner you show in which the position of the price corresponds to the validValue then you can use a List for the validValues. If the validValues are also sorted then you can use a BinarySearch but of course for just 10 items, a BinarySearch does not add much efficiency. There are other ways to search a List; have a look at the documentation.
int[] validValues = { 101, 108, 201, 213, 266, 304, 311, 409, 411, 412 };
double[] prices = { 0.89, 1.23, 3.50, 0.69, 5.79, 3.19, 0.99, 0.89, 1.26, 8.00 };
List validValuesList = new List(validValues);
//
int itemOrdered = 311;
int i = validValuesList.BinarySearch(itemOrdered);
if (i >= 0)
Console.WriteLine(prices[i]);

An alternative is a Dictionary or SortedList. I am not sure this would satisfy your requirements but it appears to and if it does then this is what an experienced developer would use.
Dictionary PricesByValues = new Dictionary();
PricesByValues[101] = 0.89;
PricesByValues[108] = 1.23;
PricesByValues[201] = 3.50;
PricesByValues[213] = 0.69;
PricesByValues[266] = 5.79;
PricesByValues[304] = 3.19;
PricesByValues[311] = 0.99;
PricesByValues[409] = 0.89;
PricesByValues[411] = 1.26;
PricesByValues[412] = 8.00;
int itemOrdered = 311;
double d;
if (PricesByValues.TryGetValue(itemOrdered, out d))
Console.WriteLine(d);
14y ago
Thank you
Vulpes14y ago
It's possible though it's not particularly elegant since you still need to maintain an index in relation to the prices array:

using System;

public class ParallelArrays
{
public static void Main()
{
int[] validValues = { 101, 108, 201, 213, 266, 304, 311, 409, 411, 412 };

double[] prices = { 0.89, 1.23, 3.50, 0.69, 5.79, 3.19, 0.99, 0.89, 1.26, 8.00 };

//parallel array

int itemOrdered = 311;

int i = 0;

foreach (int validValue in validValues)
{
if (itemOrdered == validValue) //order doesn't matter
{
Console.WriteLine(prices[i]);
}

i++;
}
Console.ReadKey();
}
}