Re: Wrote a blog post about CTFE and D

[Danny Arends]

On Thursday, 30 August 2012 at 17:40:16 UTC, Philippe Sigaud 
wrote:
On Thu, Aug 30, 2012 at 7:10 PM, Danny Arends 
<danny.are...@gmail.com> wrote:

I wrote a blog post about the stuff I've been doing last 
weekend using
CTFE.
All comments are welcome, you can find the blog post at:
http://www.dannyarends.nl/index.cgi?viewDetailed=00029

Nice article, Danny!

A few remarks:

degToRad!(float,int) 45

First, it seems like you missed a parenthesis pair?


Indeed, fixed

The compiler will be able to determine V in degToRad, you can 
call it like this:

degToRad!(float)(45)

Following bearophile's use of isFloatingPoint, you can use a 
default
value, if that's what you need most of the time:

import std.traits;
pure U degToRad(U = float, V)(in V deg) if (isFloatingPoint!U 
&& isIntegral!V)
{ return (deg * PI) / 180.0; }


Interesting, I knew about defaults but I tend to forget about 
them, when I can use them...

Then, to call it:

degToRad(45) => automatically expand to detToRad!(float,int)(45)

And the same type deduction for cordic gives you

cordic( degToRad(45) );

instead of

cordic!(float)(degToRad!(float,int) 45);

In gen_trigonometric, I think the float call should be a T:

result ~= cordic!T(degToRad!(float,int)(i), iter);


Indeed, fixed !

=>

result ~= cordic( degToRad!(T)(i), iter);

And, since you know the result's size in advance, you might 
want to
generate it at once:

T[2][] result = new (T[2][])(iter);
foreach(i; 0 .. 360)
    result[i] = cordic(degToRad!(T)(i), iter);
return result;

(no need for braces for a one-expression foreach)


Again valid point. Though the compile time benefits will be minor 
with all the memory CTFE is gobbling up anyway.

Or even, using map:

import std.algorithm, std.array;

return map!( i => cordic(degToRag!(T)(i), iter) )(result).array;

I like the map syntax, that's prob. because I've got an R 
background
where we have lapply (1D) and apply (2D)

Still I don't seem to get used to the => syntax...

Thanks for the feedback,

Gr,
Danny

If I get round to it I'll also update the code to use default 
return types.
Though I like being explicit with types, if you got them flaunt 
them...