Re: D JSON (WAT?!)
On Saturday, 26 July 2014 at 00:26:08 UTC, Ary Borenszweig wrote:
Or use Algebraic, but it currently doesn't support recursive
type definitions.
Algebraic does support recursive type definitions.
import std.variant;
alias Rec = Algebraic!(int, This*);
void main()
{
//I'm not sure why this works
auto i = Rec(Rec(Rec(1)));
i = Rec(new Rec(new Rec(1)));
}
Re: myrange.at(i) for myrange.dropExactly(i).front
On Saturday, 26 July 2014 at 00:28:32 UTC, Ary Borenszweig wrote: On 7/25/14, 6:39 PM, Jonathan M Davis wrote: On Friday, 25 July 2014 at 21:33:23 UTC, Timothee Cour via Digitalmars-d-learn wrote: Is there a function for doing this? myrange.at(i) (with meaning of myrange.dropExactly(i).front) it's a common enough operation (analog to myrange[i]; the naming is from C++'s std::vector::at) That would require a random access range, in which case you can just index directly. For a non-random access range, which you're doing would be the most direct way of doing it. - Jonathan M Davis No, the OP said the meaning was `myrange.dropExactly(i).front`, which is not a random access. Sometimes you *do* want the n-th element of a range even if the range is not a random access. That is an inherently expensive operation, so it would be a very bad idea IMHO to support it. The OP referenced vector, which has random access, and that's a completely different ballgame. In general, when operating on ranges, you should be trying to iterate over them only once and to backtrack as little as possible if you have backtrack. It's true that's not always possible, but if at() were O(n), then it would make inefficient code less obvious. I'd argue against at() working on non-random access ranges for the same reason that std.container doesn't support containers with a length property of O(n) - because it's a function that looks like it's O(1), and programmers will consistently think that it's O(1) and misuse it. C++ has had that problem with std::list' size function which is O(n). at() looks like it would be O(1) (and it always is in C++), so it would be inappropriate to have it in cases where it would need to be O(n), and since we already have [], why add at()? It exists on vector in addition to [] to give it range checking random-access. We already have that in D with []. myrange.dropExactly(i).front makes it much more obvious what you're doing and that it's inefficient. It might be necessary in some cases, but we don't want to give the impression that it's cheap, which at() would do. - Jonathan M Davis
Re: myrange.at(i) for myrange.dropExactly(i).front
On 7/25/14, 6:39 PM, Jonathan M Davis wrote: On Friday, 25 July 2014 at 21:33:23 UTC, Timothee Cour via Digitalmars-d-learn wrote: Is there a function for doing this? myrange.at(i) (with meaning of myrange.dropExactly(i).front) it's a common enough operation (analog to myrange[i]; the naming is from C++'s std::vector::at) That would require a random access range, in which case you can just index directly. For a non-random access range, which you're doing would be the most direct way of doing it. - Jonathan M Davis No, the OP said the meaning was `myrange.dropExactly(i).front`, which is not a random access. Sometimes you *do* want the n-th element of a range even if the range is not a random access.
Re: D JSON (WAT?!)
On 7/25/14, 1:06 PM, Justin Whear wrote: On Thu, 24 Jul 2014 22:00:43 +, Pavel wrote: On Thursday, 24 July 2014 at 16:09:25 UTC, Justin Whear wrote: On Thu, 24 Jul 2014 16:04:01 +, Pavel wrote: Thanks to all you folks who explained "in" operator for me. My bad. Let's focus on the real problem, which is JSON wrapper class. Is it needed? Wouldn't it be better to get AA from parseJSON? The following are valid JSON: auto json1 = parseJSON(`1`); auto json2 = parseJSON(`"foo"`); auto json3 = parseJSON(`[1, 2, 3]`); None of these fit naturally into an JSONValue[string] return type. Now we figured it out about JSON, but in that case: Why not just use std.variant.Variant construct instead of JSONValue? While I suspect the reason is simply historical, it might be a type- safety/information problem as well. Variant can store values of essentially any type whereas JSON is strictly limited to a handful of simple types. Going from a JSON string to Variant might not be troublesome, but going from Variant to JSON string almost certainly would. That said, if you think it's worth it, I'd be up for reviewing a revamped std.json. Or use Algebraic, but it currently doesn't support recursive type definitions. I think this would be the best way.
Re: Equivalent of DllMain on OSX?
Loading multiple D shared libraries isn't supported on OS X yet, see these warnings in druntime: https://github.com/D-Programming-Language/druntime/blob/master/src/rt/sections_osx.d#L198 If you only have a single D shared library, I think it's possible, you just may have to tweak dmd/druntime or your build process a bit. I think Martin Nowak or Jacob Carlborg can really answer your questions, as Martin wrote a lot of that code and Jacob seems to follow it closely, whereas I don't use OS X but looked at that code when porting to Android. It would only be a single shared library. Finally got the code publicly available: https://github.com/markisaa/presto-odbc/blob/osxCompile/driver/driver.d#L61 It should compile on OSX with a simple `make clean all` Testing would require installing the iODBC driver manager and pressing the 'Add Driver' button, possibly making a new User DSN, and possibly pressing 'Test'.
Re: Equivalent of DllMain on OSX?
On Friday, 25 July 2014 at 21:23:00 UTC, Mark Isaacson wrote: I am presently trying to port a driver I wrote for Windows to OSX. The one thing standing in my way is figuring out how to get the equivalent of DllMain on OSX. I need a place to call Runtime.initialize() and whatnot. Reading the wiki, it seemed like `shared static this()` was the appropriate construct to use, and indeed, when I run the test program from: http://dlang.org/dll-linux.html#dso9 I get the desired results: namely, I see that the `shared static this()` in that test program is called the desired point. When I try the same thing in my driver, it is never executed. Are dylibs on OSX not supported still (I saw some very old threads from 2012 stating as much)? Does it matter that I have multiple modules in the driver? Any help would be appreciated. I shall endeavor to get the modified driver code into a state where I can link it as well. Loading multiple D shared libraries isn't supported on OS X yet, see these warnings in druntime: https://github.com/D-Programming-Language/druntime/blob/master/src/rt/sections_osx.d#L198 If you only have a single D shared library, I think it's possible, you just may have to tweak dmd/druntime or your build process a bit. I think Martin Nowak or Jacob Carlborg can really answer your questions, as Martin wrote a lot of that code and Jacob seems to follow it closely, whereas I don't use OS X but looked at that code when porting to Android.
Re: myrange.at(i) for myrange.dropExactly(i).front
On Friday, 25 July 2014 at 21:33:23 UTC, Timothee Cour via Digitalmars-d-learn wrote: Is there a function for doing this? myrange.at(i) (with meaning of myrange.dropExactly(i).front) it's a common enough operation (analog to myrange[i]; the naming is from C++'s std::vector::at) That would require a random access range, in which case you can just index directly. For a non-random access range, which you're doing would be the most direct way of doing it. - Jonathan M Davis
myrange.at(i) for myrange.dropExactly(i).front
Is there a function for doing this? myrange.at(i) (with meaning of myrange.dropExactly(i).front) it's a common enough operation (analog to myrange[i]; the naming is from C++'s std::vector::at)
Equivalent of DllMain on OSX?
I am presently trying to port a driver I wrote for Windows to OSX. The one thing standing in my way is figuring out how to get the equivalent of DllMain on OSX. I need a place to call Runtime.initialize() and whatnot. Reading the wiki, it seemed like `shared static this()` was the appropriate construct to use, and indeed, when I run the test program from: http://dlang.org/dll-linux.html#dso9 I get the desired results: namely, I see that the `shared static this()` in that test program is called the desired point. When I try the same thing in my driver, it is never executed. Are dylibs on OSX not supported still (I saw some very old threads from 2012 stating as much)? Does it matter that I have multiple modules in the driver? Any help would be appreciated. I shall endeavor to get the modified driver code into a state where I can link it as well.
Re: dual with statement
On Friday, 25 July 2014 at 01:54:53 UTC, Jay Norwood wrote:
On Thursday, 24 July 2014 at 20:16:53 UTC, monarch_dodra wrote:
Or did I miss something?
Yes, sorry, I should have pasted a full example previously. The
code at the end is with the Raw_met members renamed (they were
originally a and b but clashed).
So, if Raw_met members were still a and b ...
with(ar.r as v) with (ar.rm as res){
res.a = v.a + v.c;
res.b = (v.c==0)? 0: (v.a + v.b)/ v.c;
I don't recall the exact use case for the database expressions,
but I believe they were substituting a simple symbol for the
fully qualified object. So they would have done something
analogous to this ...
Isn't:
with(foo.bar as baz) { ... }
Functionally nothing more than an alias? EG:
{
alias baz = foo.bar;
...
}
Or mix of both. I don't see a need for "as".
Re: findSplit
On Friday, 25 July 2014 at 18:56:44 UTC, Gecko wrote: findSplit accepts a predicate but it doesnt compile for me if i use an other function than ((a,b) => a == b). Not at the moment. I've been working on a patch that makes the `findSplit*` family of algorithms as powerful as `find`, including support for your use case.
findSplit
Hello,
is there a pretty way to split a range into 3 pieces, like
findSplit, just with a predicate instead of comparing it with an
element.
Like this :
void main() {
import std.algorithm, std.stdio;
auto list = [1,2,3,4,5,6,7];
writeln(findSplit!(x => x == 3 )(list));
//should print Tuple!() ([1,2], [3], [4,5,6,7])
}
findSplit accepts a predicate but it doesnt compile for me if i
use an other function than ((a,b) => a == b).
Re: D JSON (WAT?!)
On Thu, 24 Jul 2014 22:00:43 +, Pavel wrote: > On Thursday, 24 July 2014 at 16:09:25 UTC, Justin Whear wrote: >> On Thu, 24 Jul 2014 16:04:01 +, Pavel wrote: >>> >>> Thanks to all you folks who explained "in" operator for me. My bad. >>> Let's focus on the real problem, which is JSON wrapper class. Is it >>> needed? Wouldn't it be better to get AA from parseJSON? >> >> The following are valid JSON: >> >> auto json1 = parseJSON(`1`); >> auto json2 = parseJSON(`"foo"`); >> auto json3 = parseJSON(`[1, 2, 3]`); >> >> None of these fit naturally into an JSONValue[string] return type. > > Now we figured it out about JSON, but in that case: > Why not just use std.variant.Variant construct instead of JSONValue? While I suspect the reason is simply historical, it might be a type- safety/information problem as well. Variant can store values of essentially any type whereas JSON is strictly limited to a handful of simple types. Going from a JSON string to Variant might not be troublesome, but going from Variant to JSON string almost certainly would. That said, if you think it's worth it, I'd be up for reviewing a revamped std.json.
Re: Associative array to Struct at compile time
On Friday, 25 July 2014 at 15:48:54 UTC, John Colvin wrote:
On Friday, 25 July 2014 at 15:25:43 UTC, BlackEdder wrote:
Is it possible to automatically convert an associative array
to a
struct?
Basically I want to do the following (for any struct).
struct A {
double x = 1;
}
double[string] aa = ["x":1];
auto a = toStruct!A( aa );
I've been trying to do this at compile time, but can't work out
how setMembers and or loop over the associative array at
compile
time.
Is this possible at all?
one possible way:
enum aa = ["x": 1];
import std.traits;
struct AAtoStruct(alias aa)
if(isAssociativeArray!(typeof(aa)) &&
isSomeString!(KeyType!(typeof(aa
{
alias T = ValueType!(typeof(aa));
import std.range, std.algorithm, std.array;
mixin(zip(aa.keys, aa.values)
.map!`"T " ~ a[0] ~ " = " ~ a[1].to!string ~ ";\n"`
.joiner.array);
}
alias S = AAtoStruct!aa;
The associative array is actually not known at compile time. I
got it working though:
unittest {
T toStruct( T )( double[string] aa ) {
T t;
foreach (name; __traits(allMembers, T))
{
static if(
__traits(compiles, __traits(getMember, t, name))
// Skip Functions
&& !isSomeFunction!(__traits(getMember, t, name) )
)
{
mixin( "t." ~ name ~ "= aa[\"" ~ name ~ "\"];" );
}
}
return t;
}
struct A {
double x = -1;
}
double[string] aa = ["x":1];
auto a = toStruct!A( aa );
assert( a.x == 1 );
}
Re: Associative array to Struct at compile time
On Friday, 25 July 2014 at 15:25:43 UTC, BlackEdder wrote:
Is it possible to automatically convert an associative array to
a
struct?
Basically I want to do the following (for any struct).
struct A {
double x = 1;
}
double[string] aa = ["x":1];
auto a = toStruct!A( aa );
I've been trying to do this at compile time, but can't work out
how setMembers and or loop over the associative array at compile
time.
Is this possible at all?
one possible way:
enum aa = ["x": 1];
import std.traits;
struct AAtoStruct(alias aa)
if(isAssociativeArray!(typeof(aa)) &&
isSomeString!(KeyType!(typeof(aa
{
alias T = ValueType!(typeof(aa));
import std.range, std.algorithm, std.array;
mixin(zip(aa.keys, aa.values)
.map!`"T " ~ a[0] ~ " = " ~ a[1].to!string ~ ";\n"`
.joiner.array);
}
alias S = AAtoStruct!aa;
Re: Array Operations question
Márcio Martins:
float[10] a;
a[] = uniform(0.0f, 1.0f);
This is going to set all values to the result of a single call
to uniform();
Is there a way to express my intent that I want one result per
array element?
Currently D array operations can't be used for that kind of
usage. So you have to use a normal foreach loop:
void main() {
import std.stdio, std.random;
float[10] a;
foreach (ref x; a)
x = uniform01;
a.writeln;
}
Or you can also use ranges, in a functional style:
void main() {
import std.stdio, std.range, std.random, std.algorithm;
float[10] a;
a
.length
.iota
.map!(_ => uniform01)
.copy(a[]);
a.writeln;
}
Bye,
bearophile
Array Operations question
Hello! I started exploring D today and one of the things that caught my attention was the "array operations" feature. While playing around and writing some code with it, I came across a problem I wasn't able to find a solution for. The following is a simple example of the assignment array operator to initialize an array. float[10] a; a[] = uniform(0.0f, 1.0f); This is going to set all values to the result of a single call to uniform(); Is there a way to express my intent that I want one result per array element?
Re: Associative array to Struct at compile time
BlackEdder: Is this possible at all? I think it's possible, as long as your associative array contents are known at compile-time. You can write a function that given the associative array returns a string that mixed-in defines the struct. And then you can define a toStruct template. Bye, bearophile
Associative array to Struct at compile time
Is it possible to automatically convert an associative array to a
struct?
Basically I want to do the following (for any struct).
struct A {
double x = 1;
}
double[string] aa = ["x":1];
auto a = toStruct!A( aa );
I've been trying to do this at compile time, but can't work out
how setMembers and or loop over the associative array at compile
time.
Is this possible at all?
Re: dual with statement
On Friday, 25 July 2014 at 01:54:53 UTC, Jay Norwood wrote:
I don't recall the exact use case for the database expressions,
but I believe they were substituting a simple symbol for the
fully qualified object.
The sql with clause is quite a bit different than I remembered.
For one thing, I have the order reversed, so it would have been
with (a as something.x.y).
It looks more like they are more like creating a temporary tuple
from some more complicated selection. It isn't clear what the
implementation is, but just the that it might be a more concise
way of stating things so that the expressions inside the body can
be simple
So, my prior example
with (ar.rm.a as d) with (ar.rm.b as e) with (ar.r.a as a) with
(ar.r.b as b) with (ar.r.c as c){
d = a + c;
e = (c==0)?0:(a+b)/c;
}
would reduce to something maybe simpler to read. The sql seems
to be using this as a foreach type operation, but I was just
interested in the name substitution so that the expressions
inside the with block could be simpler, as well as get rid of the
struct member name clashes.
with ( (d,e,a,b,c) as (ar.rm.a, ar.rm.b, ar.r.a, ar.r.b, ar.r.c)){
d = a + c;
e = (c==0)?0:(a+b)/c;
}
Re: Mocking serial device
Hello. Just to finish this thread, umockdev[1] seems to be just what I want. Thank you for your sugestion! [1] https://github.com/martinpitt/umockdev
Trying to add automatic radix detection in std.conv.parse
hello, I'd like to test if it's possible to add an automatic
radix detection in std.conv, parse.
I've added...
if (s.length >= 2)
{
if (s[0..2] == "0x" || s[0..2] == "0X")
{
uint radix = 16;
Source nbr = s[2..$];
return .parse!Target(nbr, radix);
}
else if (s[0..2] == "0b" || s[0..2] == "0B")
{
uint radix = 2;
Source nbr = s[2..$];
return .parse!Target(nbr, radix);
}
}
...to the first parse version. The (maybe `naive`) idea is to
redirect to the right parse version if the prefixes are found.
But it seems to break the purity of format() because I get , when
compiling phobos, the following errors:
std\utf.d(71): Error: pure function 'std.utf.UTFException.this'
cannot call impure function 'std.str
ing.format!(char, uint).format'
std\utf.d(71): Error: safe function 'std.utf.UTFException.this'
cannot call system function 'std.str
ing.format!(char, uint).format'
std\uuid.d(1536): Error: pure function
'std.uuid.UUIDParsingException.this' cannot call impure funct
ion 'std.string.format!(char, string, string, uint).format'
What's wrong ?
Showing a user specified error message when no overloads match
I have a template function with a particular constraint (in this case [1]). When this constraint doesn't match, I want to give the user a suggestion what to do instead. The only way I know of to do this currently is to relax the template constraints, and adding a `static assert`. However, if there is another function that would match, this would lead to an ambiguity. Is there a way to trigger the static assert only if there are no other overloads (including members and UFCS functions) that match? Or maybe a solution that only works for this particular case? [1] https://github.com/D-Programming-Language/phobos/pull/2350
