Re: Expression transformation by symbol name
On Friday, 8 September 2017 at 13:15:51 UTC, Dominic Jones wrote: Where 'a' and 'b' are of the same type: 1. "transform(a * a)" returns an object to evaluate "2 * a" 2. "transform(a * b)" returns an object to evaluate "a * b" 1. "transform(a + a)" returns an object to evaluate "2 * a" 2. "transform(a + b)" returns an object to evaluate "a + b"
Expression transformation by symbol name
Hello, Is there a way in D of applying a transform function to the following expressions at compile-time such that the first is modified and the second left unchanged? Where 'a' and 'b' are of the same type: 1. "transform(a * a)" returns an object to evaluate "2 * a" 2. "transform(a * b)" returns an object to evaluate "a * b" Such transformations appear to be impossible without some kind of access to the symbol name in order to distinguish the two scenarios. If it is possible, what are the reflection functions one would need to use to implement this? If it is not possible, has there been any interest or attempts to add such reflection functionality to the language to make it possible? Thank you, Dominic Jones
fill array using a lambda function
Hello,
I want to fill an array with random numbers without resorting to
loops, i.e. by doing something like the following, if it were
possible:
fill!(function double(){ return uniform(0.0, 1.0);})(x[]);
Is there a simple way of doing this?
Thank you,
Dominic Jones
P.S. I am aware of the function uniformDistribution, but it makes
the sum of the elements equal to 1, which I don't want.
`Static If Considered' C++ article
Hello, A response to the static if proposal for C++ was made recently which was a rather severe critique. Has there been a response to this critique or are the conclusions of the article generally considered to be justified? I shall be attending the ACCU meeting this April and would like to raise the matter, but would first like to know the comments of those working on and with D. Thank you, Dominic Jones The article: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3613.pdf
operations on rectangular arrays
Hello, This code snippet: int[][] A = [[1, 2], [2, 3]]; int[][] B = [[2, 3], [1, 2]]; int[2][2] C; C = A[][] + B[][]; fails with the message: Error: cannot implicitly convert expression (A[][] + B[][]) of type int[][] to int[2LU][] Is there a succinct work-around (i.e. without using foreach)? And will such statements one day be possible? The section in http://dlang.org/arrays.html on rectangular arrays offers no use cases to follow. Thank you, Dominic Jones
MPI bindings revisited
Hello, A while ago a thread was started on implementing MPI bindings for D (see http://forum.dlang.org/thread/dnjm6k$145u$1...@digitaldaemon.com | Stewart Gordon; December 12, 2005; Partial translation of MPI headers; digitalmars.D.announce) I downloaded the bindings (mpi.tar.gz) and tried to compile it, but I had no success. I am too incompetent to get it working. May someone have a look into it? I (and probably many others involved in massive numerical computation) would find this binding very useful, Once working, it seems like it would fit well in Deimos. Thank you, Dominic Jones
primitive type operator overload
Hello, I want to overload a primitive type operator so that I can do something like double a; myStruct b; writeln(a + b); but have no idea how to do it. Something similar(?) is already implemented in the language, i.e. double x; double[] y; writeln(x + y); but after searching the dmd2/src, what I found didn't offer any help. -Dominic Jones
Re: FIFO stack
To conclude the matter regarding the absence of a FIFO stack in the standard library and the not so good alternative of arrays (in particular where there are a significant number of push-pops and the maximum length is not initially known): Does anyone in-the-know know if something like DList (a doubly linked list) will be added to std.containers in the near future? I, for one, would very much appreciate its implementation in the standard library. Regards, Dominic
template expressions in C++ to an equivalent in D
Hello, I want to compute, for example d = a + b + c where a..d are of some derived type, without incurring the cost of temporaries for each overloaded operation. In a similar post a while ago, Walter Bright proposed using function literals instead of template expressions to do this. After looking at function literals, I can't work out what he had in mind with this suggestion. May someone present a succinct complete example to demonstrate how solve this? Many thanks, Dominic Jones
FIFO stack
Hello, I was looking for a FIFO stack in std.containers but only found SList and Array which both appear to essentially operate as LIFO stacks. Is there any standard container with which I can push items on to a list, then later pop them off from the bottom of that list? If so, then how? Thank you, Dominic Jones
Re: FIFO stack
Also an plain array is a good stack. :) I'd rather not use a plain array because (I assume) that when I push or pop using arrays, a swap array is created to resize the original. If this is not the case, then an array will certainly do. -Dominic
facilitating automatic differentiation
I have worked on differentiating algorithms written in Fortran 90/95 using Tapenade (http://www-sop.inria.fr/tropics/tapenade.html) with moderate success. For more expressive languages the source transformation process rapidly tends towards the impossible. However, I speculate that in D some of its language features (e.g. mixin, scope) may facilitate differentiation without recourse to an external tool. I don't know D well enough, and I am not familiar with the possible trickery that can be done with such a language, but if there is someone who does have some understanding of automatic differentiation and is competent with D, I'd be very interested in your comments as to whether or not such a pursuit is worthwhile. Thank you Dominic Jones
D programs linked with C/MPI based libraries
Hello, Is it possible to call within a D driver program library functions which are programmed in C/C++ with the message passing interface (MPI)? I want to write a program which makes use of the ParMetis library (http://glaros.dtc.umn.edu/gkhome/metis/parmetis/overview). Supposing it is possible, to compile and run C/MPI programs, wrapper commands are used, such as mpicc and mpirun. What would be done in D? Thank you, Dominic Jones
intrinsic min and max for ints
Hello, Is there a library function for min/max for integers. I would rather not use the ?-operator, it's rather clumsy. I looked in the standard lib and only found f(min|max). Thank you, Dominic Jones
using a binary tree container
Hello, I have a list of strings and I want to determine whether or not a particular string in the is in that list. Assuming I should store the list of strings in a binary tree to facilitate fast searching, I had a look at the std.container documentation and found RedBlackTree, but the documentation for it has no examples. May someone offer an example of how to use it? Thank you, Dominic Jones
Re: using a binary tree container
== Quote from bearophile (bearophileh...@lycos.com)'s article Dominic Jones: I have a list of strings and I want to determine whether or not a particular string in the is in that list. What about using: size_t[sting] yourStringSet; Bye, bearophile Would that not be constructing an associated array? Whilst an associated array would do the job, there is no value for the key:value pair, just a list of keys. In the C++ STL there are the set and map containers. I want something like set. Dominic
allocating an array in an associative array
Hello, I want to allocate the int[] array for a particular key in int[][string] list; by doing list[key].length = list[key].length + 1; but it does not work. I get an array bounds error. I am using gdc 4.3.5. Any suggestions? Thank you, Dominic Jones
