Anonymous function syntax

[Andrei Alexandrescu]

On 9/23/11 8:03 PM, Martin Nowak wrote:
> On Thu, 22 Sep 2011 22:54:55 +0200, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
> I want to add some points against introducing this particular syntax.
>
> 1. Foremost using '=>' is unfamiliar. Comming from C++ or Java you
> really have to learn reading it.
> If you weighted the lambda syntaxes with the tiobe factor, arrows would
> be a minority.

Well the C++2011 lambda syntax is quite foreign for C++ users, too.

> How often have you stopped reading about a language because the code
> examples were unreadable?
> Besides my liking for haskell, I don't want to see anything close to
> this on the D site.
>
> mergesortBy less [] = []
> mergesortBy less xs = head $ until (null.tail) pairs [[x] | x <- xs]
> where
> pairs (x:y:t) = merge x y : pairs t
> pairs xs = xs
> merge (x:xs) (y:ys) | less y x = y : merge (x:xs) ys
> | otherwise = x : merge xs (y:ys)
> merge xs ys = xs ++ ys

I don't understand the point being made here.

> 2. D is not a functional language, using the implies arrow in 'a =>
> write(1, a.ptr, a.length)' creates a horribly association.

Hackeyed as that sounds, D is a multi-paradigm language and includes a 
lot of functional artifacts.

> 3. I don't see any of the proposed rewrites is working for nullary
> delegates.
> '=> foo()' ???
> Or '_ => foo()' => 'Error can't deduce parameter'.

The comma-separated list may be empty.

> 4. The expression is badly delimited.
> The first rewrite symbol => expression
> is actually symbol => expression\{CommaExpression, CatExpression}.
>
> E.g.:
> dgs ~= (int a) => (a + 5) ~ (int a) => (a ^^ 2);
> foo(a, b => (log(b), b), c)
> And that with a pending tuple syntax reclaming even more parens, comma
> overloads.

Not sure I understand this point either, sorry.

> So D is a curly bracket language.
> http://en.wikipedia.org/wiki/List_of_programming_languages_by_category#Curly-bracket_languages
>
> What is wrong the, I think earlier proposed, very simple solution.
>
> http://www.digitalmars.com/d/2.0/expression.html#FunctionLiteral
>
> FunctionLiteral:
> function Typeopt ParameterAttributes opt FunctionLiteralBody
> delegate Typeopt ParameterAttributes opt FunctionLiteralBody
> ParameterAttributes FunctionLiteralBody
> FunctionLiteralBody
>
> ParameterAttributes:
> Parameters
> Parameters FunctionAttributes
>
> FunctionLiteralBody:
> FunctionBody
> '{' Expression '}'
>
> (a, b) {a+b} // takes the same amount of characters

We've been discussing the issues of this form.


Andrei