Re: How to write similar code D?
FG:
auto query = iota(2, 2 + 10)
.map!(c => ["Length": 2 * c, "Height": c * c - 1,
"Hypotenuse": c * c + 1])
.map!(x => format("%4d%4d%4d", x["Height"],
Unlike other languages like JavaScript, the D front-end is very
weak in optimizing well such kind of code... I think D compilers
handle built-in associative arrays in a very straight way.
Bye,
bearophile
Re: How to write similar code D?
On Tuesday, 10 February 2015 at 01:31:54 UTC, FG wrote:
On 2015-02-10 at 01:41, bearophile wrote:
auto query = iota(2, 12)
.map!(c => Tuple!(int,"length", int,"height",
int,"hypotenuse")
(2 * c, c ^^ 2 - 1, c ^^ 2 +
1))
.map!(x => "%3d%4d%4d".format(x.height,
x.hypotenuse, x.length));
I took advantage of the fact that all elements were of the same
type:
auto query = iota(2, 2 + 10)
.map!(c => ["Length": 2 * c, "Height": c * c - 1,
"Hypotenuse": c * c + 1])
.map!(x => format("%4d%4d%4d", x["Height"],
x["Hypotenuse"], x["Length"]));
...
and was surprised that it worked straight away. :)
But definitely this looks better and less complicated:
auto query = iota(2, 12)
.map!(c => tuple(c ^^ 2 - 1, c ^^ 2 + 1, 2 * c));
foreach (x; query)
writefln("%4d%4d%4d", x[]);
It's the foreach version, since `each` isn't officially out yet.
Thank you.
Re: How to write similar code D?
On 2015-02-10 at 01:41, bearophile wrote:
auto query = iota(2, 12)
.map!(c => Tuple!(int,"length", int,"height",
int,"hypotenuse")
(2 * c, c ^^ 2 - 1, c ^^ 2 + 1))
.map!(x => "%3d%4d%4d".format(x.height, x.hypotenuse,
x.length));
I took advantage of the fact that all elements were of the same type:
auto query = iota(2, 2 + 10)
.map!(c => ["Length": 2 * c, "Height": c * c - 1, "Hypotenuse": c * c + 1])
.map!(x => format("%4d%4d%4d", x["Height"], x["Hypotenuse"], x["Length"]));
...
and was surprised that it worked straight away. :)
But definitely this looks better and less complicated:
auto query = iota(2, 12)
.map!(c => tuple(c ^^ 2 - 1, c ^^ 2 + 1, 2 * c));
foreach (x; query)
writefln("%4d%4d%4d", x[]);
It's the foreach version, since `each` isn't officially out yet.
Re: How to write similar code D?
Dennis Ritchie:
Tell me, please, how to write similar С# code D:
This is more or less exactly the same:
void main() {
import std.stdio, std.range, std.algorithm, std.typecons,
std.format;
auto query = iota(2, 12)
.map!(c => Tuple!(int,"length", int,"height",
int,"hypotenuse")
(2 * c, c ^^ 2 - 1, c ^^ 2 + 1))
.map!(x => "%3d%4d%4d".format(x.height,
x.hypotenuse, x.length));
foreach (immutable x; query)
x.writeln;
}
But often you write something more like this in D using the
latest version of the compiler:
void main() {
import std.stdio, std.range, std.algorithm, std.typecons;
iota(2, 12)
.map!(c => tuple(c ^^ 2 - 1, c ^^ 2 + 1, 2 * c))
.each!(x => writefln("%3d%4d%4d", x[]));
}
Bye,
bearophile
How to write similar code D?
Tell me, please, how to write similar С# code D:
using System;
using System.Linq;
public class Test
{
public static void Main()
{
var query = Enumerable.Range(2, 10)
.Select(c => new { Length = 2 * c, Height = c * c - 1,
Hypotenuse = c * c + 1 })
.Select(x => string.Format("{0,4}{1,4}{2,4}", x.Height,
x.Hypotenuse, x.Length));
foreach (var x in query)
Console.WriteLine(x);
}
}
Output:
3 5 4
8 10 6
15 17 8
24 26 10
35 37 12
48 50 14
63 65 16
80 82 18
99 101 20
120 122 22
