Re: how to define infix function
u can use infix function with 1arg without any parentheses. UPD with 2args arg1 `infix func` arg2 latter I told about UFCS with 1arg `UFCS func` arg1
Re: how to define infix function
On Saturday, 2 June 2018 at 22:01:02 UTC, Ali Çehreli wrote:
On 06/02/2018 02:44 PM, greatsam4sure wrote:
> is it possible to define infix function in D
> 3.min(5)// 3: where min is a function, works in D
> 3 min 5 // does not work.
This is called universal function call syntax (UFCS) in D.
Ali
UFCS is not same as infix functions.
infix allow to u write code like:
1)for (i in 0 to 10 step 2) // `in`(can be keyword too), `to` and
`step` can be some functions that change range or something
2) auto shiftedRes = someVar shr 13; // `shr` is infix function
too
u can use infix function with 1arg without any parentheses.
why this need? how it can be useful? look at Kotlin lang.
pure functional programming.
it can be useful for code looks like LINQ(.NET): DB, UI...
and I think UFCS should be improved too: function with 1arg can
be written without parenthesis too. for example
some declarations:
class Task { .. };
Task asyncRead( File file ) { .. }
T await!(T)( Task task ) { .. }
we can use await like:
auto buf = asyncRead( file ).await();
or
auto buf = await( asyncRead( file )); // I like spaces between
fn-names and args
but more clear IMO:
auto buf = await asyncRead( file ); // less parenthesis
more improvements:
1) see Kotlin passing lambda as last parameter
https://kotlinlang.org/docs/reference/lambdas.html#passing-a-lambda-to-the-last-parameter
2) Kotlin/when with pattern matching. dont need change current
`switch` instruction. and we can make `when` as expression (look
Kotlin samples)
3) scope functions
https://kotlinlang.org/docs/reference/scope-functions.html
with(button) { text = "hello"; background = Colors.Yellow; }
text & background are props of some Button class for instance
button. {} is a lambda as last arg
Re: how to define infix function
On Saturday, 2 June 2018 at 23:17:48 UTC, Simen Kjærås wrote:
unittest
{
import std.algorithm.comparison;
alias min = Operator!(std.algorithm.comparison.min);
assert(1 /min/ 3 == 1);
}
Why not:
alias Δ = Operator!(std.algorithm.comparison.min);
assert(1 /Δ/ 3 == 1);
To improve readibility :)
Re: how to define infix function
On Saturday, 2 June 2018 at 23:17:48 UTC, Simen Kjærås wrote:
On Saturday, 2 June 2018 at 22:09:49 UTC, Neia Neutuladh wrote:
On Saturday, 2 June 2018 at 21:44:39 UTC, greatsam4sure wrote:
Sorry for the typo
is it possible to define infix function in D
3.min(5)// 3: where min is a function, works in D
3 min 5 // does not work.
thanks in advance
This is a horrible abuse of D's operator overloading
discovered by FeepingCreature in the distant past.
You have to delimit your custom infix operator with slashes;
you can't make `3 min 5` work, but you can make `3 /min/ 5`
work.
Observe:
struct Min
{
MinIntermediate!T opBinaryRight(string op, T)(T value) if
(op == "/")
{
return MinIntermediate!T(value);
}
}
struct MinIntermediate(T)
{
T value;
T opBinary(string op, T)(T value2) if (op == "/")
{
if (value < value2) return value;
return value2;
}
}
Min min;
void main()
{
writeln(1 /min/ 2);
}
And of course, this can be generalized:
struct Operator(alias fn, string operator = "/")
{
static auto opBinaryRight(string op : operator, T...)(T
value1)
{
struct Result
{
auto opBinary(string op : operator, U...)(U value2)
if (__traits(compiles, fn(value1, value2)))
{
return fn(value1, value2);
}
}
Result result;
return result;
}
}
unittest
{
import std.algorithm.comparison;
alias min = Operator!(std.algorithm.comparison.min);
assert(1 /min/ 3 == 1);
}
Note also the use of static opBinaryRight, allowing one to
eschew the 'min' variable.
All of this said, I would suggest not using this in prod - it's
a neat trick that shows off some of D's power, but I don't see
a case where this would be easier to understand than a
straightforward function call.
--
Simen
That is interesting. I don't know yet whether it's good or bad,
but certainly, it's interesting.
Re: how to define infix function
On Saturday, 2 June 2018 at 22:09:49 UTC, Neia Neutuladh wrote:
On Saturday, 2 June 2018 at 21:44:39 UTC, greatsam4sure wrote:
[...]
This is a horrible abuse of D's operator overloading discovered
by FeepingCreature in the distant past.
You have to delimit your custom infix operator with slashes;
you can't make `3 min 5` work, but you can make `3 /min/ 5`
work.
Observe:
struct Min
{
MinIntermediate!T opBinaryRight(string op, T)(T value) if
(op == "/")
{
return MinIntermediate!T(value);
}
}
struct MinIntermediate(T)
{
T value;
T opBinary(string op, T)(T value2) if (op == "/")
{
if (value < value2) return value;
return value2;
}
}
Min min;
void main()
{
writeln(1 /min/ 2);
}
thanks
Re: how to define infix function
On Saturday, 2 June 2018 at 22:09:49 UTC, Neia Neutuladh wrote:
On Saturday, 2 June 2018 at 21:44:39 UTC, greatsam4sure wrote:
Sorry for the typo
is it possible to define infix function in D
3.min(5)// 3: where min is a function, works in D
3 min 5 // does not work.
thanks in advance
This is a horrible abuse of D's operator overloading discovered
by FeepingCreature in the distant past.
You have to delimit your custom infix operator with slashes;
you can't make `3 min 5` work, but you can make `3 /min/ 5`
work.
Observe:
struct Min
{
MinIntermediate!T opBinaryRight(string op, T)(T value) if
(op == "/")
{
return MinIntermediate!T(value);
}
}
struct MinIntermediate(T)
{
T value;
T opBinary(string op, T)(T value2) if (op == "/")
{
if (value < value2) return value;
return value2;
}
}
Min min;
void main()
{
writeln(1 /min/ 2);
}
And of course, this can be generalized:
struct Operator(alias fn, string operator = "/")
{
static auto opBinaryRight(string op : operator, T...)(T
value1)
{
struct Result
{
auto opBinary(string op : operator, U...)(U value2)
if (__traits(compiles, fn(value1, value2)))
{
return fn(value1, value2);
}
}
Result result;
return result;
}
}
unittest
{
import std.algorithm.comparison;
alias min = Operator!(std.algorithm.comparison.min);
assert(1 /min/ 3 == 1);
}
Note also the use of static opBinaryRight, allowing one to eschew
the 'min' variable.
All of this said, I would suggest not using this in prod - it's a
neat trick that shows off some of D's power, but I don't see a
case where this would be easier to understand than a
straightforward function call.
--
Simen
Re: how to define infix function
On Saturday, 2 June 2018 at 22:01:02 UTC, Ali Çehreli wrote:
On 06/02/2018 02:44 PM, greatsam4sure wrote:
> is it possible to define infix function in D
>
> 3.min(5)// 3: where min is a function, works in D
> 3 min 5 // does not work.
This is called universal function call syntax (UFCS) in D. The
idea is simple: You can pull the first argument out as if the
function is a member function of that argument. So, in your
case it already works because there is already a min() function
that works with two (actually, many) parameters:
import std.algorithm;
void main() {
assert(min(3, 5) == 3);
assert(3.min(5) == 3);
}
However, many people don't like overusing it; it works well
only in cases where the first parameter is arguably the "main
character" in the operation. For example, min doesn't look good
because all parameters have equal roles in that function.
Ali
Thanks for your reply to my question.
Your book: programming in D is real a great help learning D. I
will appreciate it if your can expand the book to advance use of
D. That is, dealing with D advance use Case. I discover that the
D language is very advance but I am lock in the elementary yet
don't know the way out. This is because D is the most Higher
programming language that I ever use. Better still you can direct
me to more materials about D. I am already familiar will all D
books.
thanks
Re: how to define infix function
On Saturday, 2 June 2018 at 21:44:39 UTC, greatsam4sure wrote:
Sorry for the typo
is it possible to define infix function in D
3.min(5)// 3: where min is a function, works in D
3 min 5 // does not work.
thanks in advance
This is a horrible abuse of D's operator overloading discovered
by FeepingCreature in the distant past.
You have to delimit your custom infix operator with slashes; you
can't make `3 min 5` work, but you can make `3 /min/ 5` work.
Observe:
struct Min
{
MinIntermediate!T opBinaryRight(string op, T)(T value) if (op
== "/")
{
return MinIntermediate!T(value);
}
}
struct MinIntermediate(T)
{
T value;
T opBinary(string op, T)(T value2) if (op == "/")
{
if (value < value2) return value;
return value2;
}
}
Min min;
void main()
{
writeln(1 /min/ 2);
}
Re: how to define infix function
On 06/02/2018 02:44 PM, greatsam4sure wrote:
> is it possible to define infix function in D
>
> 3.min(5)// 3: where min is a function, works in D
> 3 min 5 // does not work.
This is called universal function call syntax (UFCS) in D. The idea is
simple: You can pull the first argument out as if the function is a
member function of that argument. So, in your case it already works
because there is already a min() function that works with two (actually,
many) parameters:
import std.algorithm;
void main() {
assert(min(3, 5) == 3);
assert(3.min(5) == 3);
}
However, many people don't like overusing it; it works well only in
cases where the first parameter is arguably the "main character" in the
operation. For example, min doesn't look good because all parameters
have equal roles in that function.
Ali
