在其他语言的“块值”的C＃中等效

Question

In some languages, almost everything can be used as a value. For example, some languages let you treat a block of code as a unit which can return a value.

In Scheme, a block of code wrapped in a let can return a value:

(define val
  (let ()
    (define a 10)
    (define b 20)
    (define c (+ a b))
    c))

Perl 5 also supports blocks as values:

my $val = do
{
    my $a = 100;
    my $b = 200;
    my $c = $a + $b;
    $c;
};

The closest approximation to block values I could come up with in C# was to use a lambda that is cast and immediately called:

var val = ((Func<int>)(() =>
{
    var a = 10;
    var b = 20;
    var c = a + b;
    return c;
}))();

That's not too bad and is in fact exactly what is happening semantically with Scheme; the let is transformed to a lambda which is applied. It's at this point that I wouldn't mind macros in C# to clean up the syntactic clutter.

Is there an another way to get "block values" in C#?

Answer 1

Sorry, at first I seemed to have misread your question, but it seems delegates (as in your question) are exactly what you are looking for no? If you are interested in quickly grouping a set of different values together, and not necessarily logic, my previous answer still applies.

---

C# supports anonymous types .

var v = new { Amount = 108, Message = "Hello" };

The var keyword is introduced so you don't have to specify a type name.

Afterwards you can access the members as follows:

Console.WriteLine( v.Amount );

---

Another solution since C# 4.0 is using Tuples which basically group a set of unnamed values together.

var population = Tuple.Create(
    "New York", 7891957, 7781984,
    7894862, 7071639, 7322564, 8008278 );

You have to access them using population.Item1 , population.Item2 , ...

Answer 2

In some languages, almost everything can be used as a value.

You give 1 example, Scheme. Scheme is a functional language, (almost) everything in Scheme is a function rather than a value.

C# is now partially a functional language through the inclusion of Linq.

So the equivalents you seek are Linq queries and indeed lambda functions. If that's not enough, take a look at F#.