Re: Defining an alias to an overloaded function
On Monday, 20 January 2020 at 22:02:54 UTC, olvy wrote:
I'm learning D, and as an exercise, I'm trying to define a
HashSet that would be a wrapper around an associative array
with some dummy value type.
This seems to work:
...
struct RangeImpl(T) {
alias byKeyRetType =
typeof(byKey!(int[T])((int[T]).init));
byKeyRetType keyRange;
this(ref int[T] d) {
keyRange = d.byKey;
}
bool empty() {
return keyRange.empty;
}
...
}
RangeImpl!T opSlice() {
return RangeImpl!T(_dict);
}
}
void main()
{
...
if (h[].all!(nn => nn < 5)) {
writeln("less than 5");
}
Re: Type Inference and Try Blocks
On Monday, 20 January 2020 at 23:16:07 UTC, Henry Claesson wrote:
This isn't a D-specific "problem", but there may be D-specific
solutions.
I have a function `doSomething()` that returns a Voldemort
type, and this same function also throws. So, there's this:
try {
auto foo = doSomething();
} catch (AnException e) {
// Do stuff
}
The problem that I'm encountering is that I'd like, assuming no
exception was thrown, to use foo outside the `try` (or
`finally`) block to avoid nesting as any operations on `foo`
from that point onward may also throw. Are there any constructs
that act as alternatives to try/catch/finally so that I can do
this?
(This issue could very well stem from poor design and not being
familiar with programming using exceptions. So feel free to
ignore.)
Thanks
The problem you have is not called type inference, it's called
"scope".
In a particular scope you have symbols "S". In a sub scope you
also have "S" but in the parent scope "S" are not existing
anymore.
Re: Type Inference and Try Blocks
On Monday, 20 January 2020 at 23:16:07 UTC, Henry Claesson wrote:
This isn't a D-specific "problem", but there may be D-specific
solutions.
I have a function `doSomething()` that returns a Voldemort
type, and this same function also throws. So, there's this:
try {
auto foo = doSomething();
} catch (AnException e) {
// Do stuff
}
I'd suggest just doing
try {
auto foo = doSomething();
// use foo right here!
} catch(AnException e) {
// do other stuff
} catch(OtherException e) {
// reminder you can do this too btw
}
That is, put ALL the use of foo inside the one try block, don't
keep nesting - only try/catch when you can specifically recover
or add information to it at that particular point. If you can't
do that, just keep going. try/catch over individual functions is
often (though not always) poor design.
If you really do need the variable outside, you can do
typeof(doSomething(args...)) foo;
try {
foo = doSomething()
}
too to declare the var outside. But first I'd try getting it all
in that try block.
You can also do helper functions for some cases too btw
auto getfoo() {
try return doSomething();
catch(MyException e) { return alternative(); }
}
and remember you can define that right inside the function;
nested functons rock.
Type Inference and Try Blocks
This isn't a D-specific "problem", but there may be D-specific
solutions.
I have a function `doSomething()` that returns a Voldemort type,
and this same function also throws. So, there's this:
try {
auto foo = doSomething();
} catch (AnException e) {
// Do stuff
}
The problem that I'm encountering is that I'd like, assuming no
exception was thrown, to use foo outside the `try` (or `finally`)
block to avoid nesting as any operations on `foo` from that point
onward may also throw. Are there any constructs that act as
alternatives to try/catch/finally so that I can do this?
(This issue could very well stem from poor design and not being
familiar with programming using exceptions. So feel free to
ignore.)
Thanks
Re: dub dustmite struggles
On Monday, 20 January 2020 at 15:04:32 UTC, Andre Pany wrote: In general dub Dustmite works fine, I used it several times. Maybe it has to do s.th. with your project structure. Please create a dub issue with an example zip. I've created a minimal nested project with a similar structure (library with nested app project), and dub-dustmite works fine there. So it must be something peculiar to my real project. Once the standalone dustmite finishes running, I'll spend some time manually reducing my project structure to something repeatable to file an issue with. Thanks!
Defining an alias to an overloaded function
I'm learning D, and as an exercise, I'm trying to define a
HashSet that would be a wrapper around an associative array with
some dummy value type.
This worked fine until I've tried writing opSlice for this
HashSet in terms of the byKey() function of the AA. I defined my
own internal type that wraps the one returned by byKey and
returned it. However I had to keep byKey's result inside my
internal type, but I couldn't figure out how to name it properly
without getting a compilation error.
The problem is that byKey is overloaded and but I can't figure
out how to convince the compiler to disambiguate between the
overloads.
Another lesser problem is that I have to write "opSlice"
explicitly at the call site instead of using []. But it might
be that the compiler is confused due to failure of parsing the
function.
My aim isn't building a HashSet, the point is learning, here
specifically learning how to convince the compiler to use the
correct byKey overload in this case.
I could also trivially use the AA's keys() function to implement
opSlice. But I like byKey since it exposes just an iterator,
while keys() actually allocates an array which isn't necessary
here.
I'm using dmd 2.089 on my machine.
My code is (also in https://wandbox.org/permlink/zXsf7sQiKDj6zjlJ)
import std;
struct HashSet(T) {
int[T] _dict;
bool add(T val) {
auto prev = val in _dict;
_dict[val] = 0;
return prev is null;
}
bool remove(T val) {
return _dict.remove(val);
}
bool opBinaryRight(string op)(T val) {
static if (op == "in") {
return (val in _dict) !is null;
} else {
static assert(false, "Operator " ~ op ~ " not
implemented");
}
}
import std.traits;
import std.meta;
struct RangeImpl(T) {
// Next line has compilation error since byKey has 2
overloads
alias byKeyAlias = Alias!(byKey!(int[T])(T.init));
ReturnType!(byKeyAlias) keyRange;
// alias byKeyAlias = byKey;
// ReturnType!(byKey!(int[T], T, int)) keyRange;
this(ref int[T] d) {
keyRange = d.byKey();
}
bool empty() const {
return keyRange.empty;
}
ref T front() {
return keyRange.front;
}
void popFront() {
keyRange.popFront();
}
}
// T[] opSlice(T)() {
// return _dict.keys;
// }
RangeImpl!T opSlice(T)() {
return RangeImpl!T(_dict);
}
}
void main()
{
HashSet!long h;
h.add(0);
h.add(1);
if (1 in h) {
writeln("it is");
}
if (h.opSlice!long.all!(nn => nn < 5)) {
writeln("less than 5");
}
}
Re: dub dustmite struggles
On Monday, 20 January 2020 at 06:48:08 UTC, DanielG wrote: I can't seem to figure out what dub's dustmite command is looking for with its regexes. No matter what I try - no matter how simple - the initial test fails. I am able to run dustmite standalone just fine with the following test script: cd example dub 2>&1 | grep -F "ScrollView6__initZ+0xd8): undefined reference to \`internal'" However, when I attempt using 'dub dustmite' with --linker-regex (or --linker-status, even), the initial test always fails. I've also tried simplifying the regex on the assumption that I'm not escaping things properly - to no avail. Is it perhaps something to do with my project structure? My project is a library containing an /example subfolder, containing an application dub project, and that's where my linker error occurs, not in the library itself. So that's where I'm attempting to run dub dustmite as well. In general dub Dustmite works fine, I used it several times. Maybe it has to do s.th. with your project structure. Please create a dub issue with an example zip. But yes, it could take also with dub a lot of time. One thing which caused me a lot of headaches, dmd is lies about the error message if coloured output is on. Then the error text lacks some characters. Kind regards Andre
Re: Specify dmd or ldc compiler and version in a json dub file?
On Monday, 20 January 2020 at 11:54:43 UTC, Bastiaan Veelo wrote: On Tuesday, 8 August 2017 at 09:17:02 UTC, data pulverizer wrote: I would like to know how to specify dmd or ldc compiler and version in a json dub file. Update: you can at least specify these in the toolchain requirements section: https://dub.pm/package-format-json.html#toolchain-requirements I myself am looking for ways to satisfy these automatically, using a tool like dvm (https://code.dlang.org/packages/dvm) in preBuildCommands. Bastiaan. In the meantime, the dub settings json could also be placed in the project folder and has precedence. Although I would not recommend to distribute the file as it is meant for your local working computer. Kind regards Andre
Re: Specify dmd or ldc compiler and version in a json dub file?
On Tuesday, 8 August 2017 at 09:17:02 UTC, data pulverizer wrote: I would like to know how to specify dmd or ldc compiler and version in a json dub file. Update: you can at least specify these in the toolchain requirements section: https://dub.pm/package-format-json.html#toolchain-requirements I myself am looking for ways to satisfy these automatically, using a tool like dvm (https://code.dlang.org/packages/dvm) in preBuildCommands. Bastiaan.
