internal static Fallible <TSource> ReduceImpl <TSource>(
this IEnumerable <TSource> source,
Func <TSource, TSource, Fallible <TSource> > accumulator,
Func <Fallible <TSource>, bool> predicate)
{
Debug.Assert(source != null);
Debug.Assert(accumulator != null);
Debug.Assert(predicate != null);
using (var iter = source.GetEnumerator())
{
if (!iter.MoveNext())
{
throw new InvalidOperationException("Source sequence was empty.");
}
Fallible <TSource> retval = Fallible <TSource> .η(iter.Current);
while (predicate(retval) && iter.MoveNext())
{
retval = retval.Bind(val => accumulator(val, iter.Current));
}
return(retval);
}
}
internal static Fallible <IEnumerable <TSource> > CollectImpl <TSource>(
this IEnumerable <Fallible <TSource> > source)
{
Debug.Assert(source != null);
var seed = Fallible <IEnumerable <TSource> > .η(Enumerable.Empty <TSource>());
Func <IEnumerable <TSource>, TSource, IEnumerable <TSource> > append
= (seq, item) => seq.Append(item);
var accumulator = Fallible.Lift <IEnumerable <TSource>, TSource, IEnumerable <TSource> >(append);
return(source.Aggregate(seed, accumulator));
}
internal static Fallible <IEnumerable <TSource> > WhereImpl <TSource>(
this IEnumerable <TSource> source,
Func <TSource, Fallible <bool> > predicate)
{
Debug.Assert(source != null);
Debug.Assert(predicate != null);
var seed = Fallible <IEnumerable <TSource> > .η(Enumerable.Empty <TSource>());
Func <TSource, Func <bool, IEnumerable <TSource>, IEnumerable <TSource> > > func
= item => (b, seq) => b?seq.Append(item) : seq;
Func <Fallible <IEnumerable <TSource> >, TSource, Fallible <IEnumerable <TSource> > > accumulator
= (mseq, item) => predicate(item).ZipWith(mseq, func(item));
return(source.Aggregate(seed, accumulator));
}
internal static Fallible <TAccumulate> FoldImpl <TSource, TAccumulate>(
this IEnumerable <TSource> source,
TAccumulate seed,
Func <TAccumulate, TSource, Fallible <TAccumulate> > accumulator)
{
Debug.Assert(source != null);
Debug.Assert(accumulator != null);
Fallible <TAccumulate> retval = Fallible <TAccumulate> .η(seed);
using (var iter = source.GetEnumerator())
{
while (iter.MoveNext())
{
retval = retval.Bind(val => accumulator(val, iter.Current));
}
}
return(retval);
}
