static IEnumerable <IEnumerable <T> > Transpose <T>(this IEnumerable <IEnumerable <T> > matrix)
{
return(matrix.Count() == 0 ?
ZipEnumerable.Return(Enumerable.Empty <T>()) :
from xs in matrix.First()
join xss in Transpose(matrix.Skip(1)) on 1 equals 1
select Enumerable.Concat(new[] { xs }, xss));
}
static void Main(string[] args)
{
var prices = new[] {
new[] { 10.0, 4.0, 13.0, 20.0 },
new[] { 12.0, 3.0, 11.0, 25.0 },
new[] { 9.0, 1.0, 16.0, 24.0 },
};
// Calculating average stock prices using idioms (directly)
var res1 = ZipEnumerable.Return(0.0);
foreach (var day in prices)
{
res1 = res1.Merge(day).Select(tup => tup.Item1 + tup.Item2);
}
var avg1 = res1.Select(sum => sum / prices.Count());
// Calculating average stock prices using idioms (LINQ)
var res = ZipEnumerable.Return(0.0);
foreach (var day in prices)
{
res = from sum in res
join price in day on 1 equals 1
select sum + price;
}
var avg = from sum in res select sum / prices.Count();
foreach (var price in avg)
{
Console.Write("{0}, ", price);
}
// Matrix transposition example
var matrix = new[] {
new[] { 1, 2, 3 },
new[] { 10, 20, 30 },
new[] { 100, 200, 300 }
};
var transposed = matrix.Transpose();
foreach (var a in transposed)
{
foreach (var b in a)
{
Console.Write("{0}, ", b);
}
Console.WriteLine();
}
}
// Two versions of the Transpose operation based on
// ZipList idiom using IEnumerable<T>. One version is written
// directly and the other one uses LINQ syntax with 'join'
#region Transpose from the blog post
static IEnumerable <IEnumerable <T> > Transpose2 <T>(this IEnumerable <IEnumerable <T> > matrix)
{
if (matrix.Count() == 0)
{
return(ZipEnumerable.Return(Enumerable.Empty <T>()));
}
else
{
return
(ZipEnumerable.
Merge(matrix.First(), Transpose(matrix.Skip(1))).
Select(tuple =>
Enumerable.Concat(new[] { tuple.Item1 }, tuple.Item2)));
}
}