/// <summary>
/// Groups element into sub-lists of adjacent that share the same property, true or false, from the predicate.
/// Basically performs edge detection in order to operate.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="elements"></param>
/// <param name="predicate"></param>
/// <returns></returns>
public static IEnumerable <Tuple <IEnumerable <T>, bool> > ClusteredByPredicate <T>(this IEnumerable <T> elements, Func <T, bool> predicate)
{
// We'll build a list assigning numeric, so we can have true, false AND "added at the front" for edge detection purposes.
var withTrueFalseAsOneZero = Alg.ReadPoint(elements.Select(x => Tuple.Create(x, predicate(x) ? 1 : 0))).TakenToEnd();
return(Alg.Map(
(c, prior) =>
{
var cf = c.First();
return Alg.When(
cf.Item2 != prior.Item2,
() => Tuple.Create(c.TakeWhile(x => x.Item2 == cf.Item2).Select(x => x.Item1), (cf.Item2 == 1)));
},
withTrueFalseAsOneZero.Tails().Where(x => x.Any()), new[] { Tuple.Create(default(T), -1) }.Concat(withTrueFalseAsOneZero)).SelectMany(x => x.ToEnumerable()));
}
public static IEnumerable <IEnumerable <T> > Transpose <T>(this IEnumerable <IEnumerable <T> > original)
{
var orp = Alg.ReadPoint(original);
if (!orp.AtEnd)
{
int numHorizontalInOriginal = orp.Value.Count();
// We cache this
var originalsAsArrays = Alg.ReadPoint(original.Select(row => { var r = row.ToArray(); if (r.Length != numHorizontalInOriginal)
{
throw new Exception("Row size mismatch");
}
return(r); })).TakenToEnd();
return(Enumerable.Range(0, numHorizontalInOriginal).Select(ordinal => originalsAsArrays.Select(row => row[ordinal])));
}
return(new IEnumerable <T>[] { });
}
public static IEnumerable <string> CharsToLines(IEnumerable <char> chars)
{
List <char> accumulator = new List <char>();
ReadPoint <char> currentChar = Alg.ReadPoint(chars);
while (!currentChar.AtEnd)
{
char c = currentChar.Value;
if (c == '\n')
{
yield return(Alg.MergedChars(accumulator));
accumulator = new List <char>();
}
else
if (c == '\r')
{ // have to handle '\r'-only case.
if (!currentChar.Next.AtEnd)
{
if (currentChar.Next.Value != '\n')
{
yield return(Alg.MergedChars(accumulator));
accumulator = new List <char>();
}
}
}
else
{
accumulator.Add(c);
}
currentChar = currentChar.Next;
}
if (accumulator.Count != 0)
{
yield return(Alg.MergedChars(accumulator));
accumulator = new List <char>();
}
}
public static IEnumerable <string> LineToCSFEntries(string line, char delimiter, bool quotesHaveMeaning)
{
ReadPoint <char> currentChar = Alg.ReadPoint(line.ToCharArray());
List <char> accumulatedElement = new List <char>();
bool inQuote = false;
bool haveSeenAComma = false;
while (!currentChar.AtEnd)
{
char c = currentChar.Value;
if (inQuote)
{
if (c == '\"')
{ // may be a double-quote
if (IsAtCSVQuote(currentChar))
{
accumulatedElement.Add('\"');
currentChar = currentChar.Next; // next add will be done at end of this loop.
}
else
{
accumulatedElement.Add(c);
inQuote = false;
}
}
else
{
accumulatedElement.Add(c);
}
}
else
{
if (c == delimiter)
{
haveSeenAComma = true;
yield return(Alg.MergedChars(accumulatedElement).Trim());
accumulatedElement = new List <char>();
}
else
{
if (quotesHaveMeaning && (c == '\"'))
{
inQuote = true;
accumulatedElement.Add(c);
}
else
{
accumulatedElement.Add(c);
}
}
}
currentChar = currentChar.Next;
}
if ((accumulatedElement.Count != 0) || haveSeenAComma)
{
yield return(Alg.MergedChars(accumulatedElement).Trim()); // deliberately return "last"
accumulatedElement = new List <char>();
}
}
public static IEnumerableReenumerable <T> Memoized <T>(this IEnumerable <T> source)
{
return(Alg.ReadPoint(source).TakenToEnd());
}
public static IEnumerableReenumerable <T> ShuffledWithWeights <T>(this IEnumerable <T> source, Func <T, int> weightAccess, Func <int, int> random)
{
return(Alg.ReadPoint(ShuffledAssist(source, weightAccess, random)).TakenToEnd());
}
// Memoizes/caches its result, subsequent scans of the same result will give the same sequence.
public static IEnumerableReenumerable <T> Shuffled <T>(this IEnumerable <T> source, Func <int, int> random)
{
// standard shuffle: everything has a weight of 1
return(Alg.ReadPoint(ShuffledAssist(source, item => 1, random)).TakenToEnd());
}
public static IEnumerable <IEnumerable <T> > Tails <T>(this IEnumerable <T> original)
{
return(Alg.ReadPoint(original).AllReadPointsDownIncludingEnd().Select(x => x.TakenToEnd()));
}