public static void LinqWriterTest()
{
var cxt = new WriterCxt <IList <string>, Monoid.ListAppendImmutableMonoid <string> >();
bool m = true;
var computation =
from _1 in MaybeT.Lift(cxt.Tell(FuncList.Make("function call 1")))
from _2 in MaybeT.Lift(cxt.Tell(FuncList.Make("function call 2")))
from _3 in MaybeT.HoistWriter(cxt, Maybe.JustIf(m, () => new Unit()))
from _4 in MaybeT.Lift(cxt.Tell(FuncList.Make("function call 3")))
select 5;
var value = computation.Run;
Assert.True(value.Result.HasValue);
Assert.Equal(5, value.Result.Value());
Assert.Equal(new[] { "function call 1", "function call 2", "function call 3" }, (IEnumerable <string>)value.State);
m = false;
computation =
from _1 in MaybeT.Lift(cxt.Tell(FuncList.Make("function call 1")))
from _2 in MaybeT.Lift(cxt.Tell(FuncList.Make("function call 2")))
from _3 in MaybeT.HoistWriter(cxt, Maybe.JustIf(m, () => new Unit()))
from _4 in MaybeT.Lift(cxt.Tell(FuncList.Make("function call 3")))
select 5;
value = computation.Run;
Assert.False(value.Result.HasValue);
Assert.Equal(new[] { "function call 1", "function call 2" }, (IEnumerable <string>)value.State);
}
HoistWriter <TOutput, TMonoid, TValue>(
WriterCxt <TOutput, TMonoid> _cxt,
Maybe <TValue> value)
where TMonoid : IMonoid <TOutput>
{
var m = new MaybeT <Writer <TOutput, TValue, TMonoid>, Writer <TOutput, Maybe <TValue>, TMonoid>, Maybe <TValue>, TValue>();
return((MaybeT <Writer <TOutput, TValue, TMonoid>, Writer <TOutput, Maybe <TValue>, TMonoid>, Maybe <TValue>, TValue>)m.Hoist(value));
}
