Posts Tagged ‘D Programming Language’


Removing elements from dynamic arrays in D

Removing elements from associative arrays in D is easy, as we can use the handy “remove” method. When it comes to regular dynamic arrays, however, the story is a little different. There is no such method for removing elements and the documentation doesn’t make it completely obvious.

To complicate the situation more, the technique required depends on the version of D you are using.
DMD version 2.060 is out and with it comes the deprecation of std.algorithm.indexOf. Instead, std.algorithm.countUntil should be used in its place.

Here is an example:

import std.stdio;
import std.algorithm;

void main(string[] args) {

	auto items= ["item1", "item2", "item3"];
	auto index = countUntil(items, "item2");
	writefln("Index of 'item2' is: %d", index);
	auto mutated = remove(items, index);


It generates the following output:

["item1", "item2", "item3"]
Index of 'item2' is: 1
["item1", "item3"]

QTD compile error using DMD (Solved)

I’ve just been struggling to build QTD on my Ubuntu box.  QTD is the D programming language binding for the QT framework.  The error I was getting was:

CMake Error at cmake/FindD.cmake:41 (message):
  D compiler is not found
Call Stack (most recent call first):
  CMakeLists.txt:65 (FIND_PACKAGE)

This is strange because DMD is installed. After some investigation I found that the compiler isn’t found because the cmake file (cmake/FindD.cmake) searches for the version using a regex in the output to “dmd” (around line 13):

string(REGEX MATCH "(Digital Mars|DMD32) D Compiler v[0-9]\\.[0-9]+" dmd_version "${d_output}")

This is the guilty line. When I type “dmd” on my command line, the first line looks like this:

DMD64 D Compiler v2.060

This clearly doesn’t match the above regex. To fix the problem you can modify the regex above in the file “cmake/FindD.cmake” to look like the following:

string(REGEX MATCH "(Digital Mars|DMD32|DMD64) D Compiler v[0-9]\\.[0-9]+" dmd_version "${d_output}")

This fixes the problem.


Regex Performance in D Programming Language

Note: The problem described in this post was for DMD v2.054 and it no longer occurs with the more recent DMD v2.058  (see below for details or view the discussion at the D Forums).

I am currently working on a Ruby project that uses a lot of regexes on large volumes of text.  It is currently running too slowly, so I decided to try to optimise it by implementing the regex matching code in the D programming language.  D has given me a lot of joy (compared to C or C++)  by making things like string (with Unicode) handling a breeze without taking the performance hit of supposed “productivity” languages.  I painstakingly reimplemented my Ruby functions in D expecting a huge performance boost (actually I expected an order of magnitude performance jump) but instead I was shocked to see that Ruby outperformed my D code by a significant margin.  The Ruby implementation was finished after 80 seconds, whereas the D program required around 280 seconds using the exact same regexes and the exact same input.