I am receiving a dictionary from a C# dll to C++/CLI code. I am trying to convert dictionary into std::map which will be further used by old C++ code. but I am not able to do. I have a function which is will take dictionary as parameter and return a map.
This is what I am trying to do-
std::map < std::wstring, std::map<int, int>> Convert(Dictionary<String^, Dictionary<int, int>^>^ myMap)
{
std::map < std::wstring, std::map<int, int>> h_result;
for (std::wstring& stringKey : myMap->Keys)
{
for (std::pair<int, int> intKey : (myMap->Values))
{
h_result.insert(stringKey, intKey);
}
}
return h_result;
}
I am getting error while iterating the values.
error:this range-based 'for' statement requires a suitable "begin" function and none was found
Can anybody tell what is the problem here? or if there is any better way to convert Dictionary^ into std::map, please do suggest me.
I am new with dictionary and std::map. please let me know if there is any silly mistake with the sample code.
You're (a) trying to use C++ range-for loops with Dictionary^, and (b) trying to use System types interchangeably with C++ standard types. All of which won't work.
You need to do this a bit more step-by-step: iterate the Dictionary^ collections with for each, convert the String^ to std::wstring properly, and create the map items with std::make_pair.
So your function will look something like this (untested)
std::map <std::wstring, std::map<int, int>> Convert(Dictionary<String ^, Dictionary<int, int>^> ^myMap)
{
std::map <std::wstring, std::map<int, int>> h_result;
// iterate the outer dictionary
for each(KeyValuePair<String ^, Dictionary<int, int>^> ^kvp1 in myMap)
{
std::wstring stringKey = marshal_as<std::wstring>(kvp1->Key);
std::map<int, int> mapValues;
// iterate the inner dictionary
for each(KeyValuePair<int, int> ^kvp2 in kvp1->Value)
{
// insert in inner map
mapValues.insert(std::make_pair(kvp2->Key, kvp2->Value));
}
// insert in outer map
h_result.insert(std::make_pair(stringKey, mapValues));
}
return h_result;
}
Related
I was reading the c++'s foreach syntax on MSDN:
// for_each_string1.cpp
// compile with: /ZW
#include <stdio.h>
using namespace Platform;
ref struct MyClass {
property String^ MyStringProperty;
};
int main() {
String^ MyString = ref new String("abcd");
for each ( char c in MyString )
wprintf("%c", c);
wprintf("/n");
MyClass^ x = ref new MyClass();
x->MyStringProperty = "Testing";
for each( char c in x->MyStringProperty )
wprintf("%c", c);
}
I tried to find what the "^" means on google but I couldn't find anything (or my query wasn't correct)
What does it mean? Is it as a "*"? Is it as a "&"?
This syntax also applies to C#. Do they mean the same thing in both languages?
Piece of C# code:
using namespace System;
int main(){
array<int>^ arr = gcnew array<int>{0,1,2,5,7,8,11};
int even=0, odd=0;
for each (int i in arr) {
if (i%2 == 0)
even++;
else
odd++;
}
Console::WriteLine(“Found {0} Odd Numbers, and {1} Even Numbers.”,
odd, even);
}
The "^" denotes a managed reference, which is used for managed types. It's like a pointer, but for managed types. The syntax doesn't exist in C#. In C#, the equivalent is just a variable of a reference type (as opposed to a value type), or a boxed value type.
As others have said, this is C++/CLI syntax which means you have to compile with the /clr option. C++/CLI is basically C++ with features of C# (or more generally, .NET).
https://learn.microsoft.com/en-us/cpp/extensions/handle-to-object-operator-hat-cpp-component-extensions?view=vs-2019 hope this link can help you.
btw,^ is a special character and ignored by google search engine so you can not search that.
I am completely new to C++, so I'm stuck on something which I'm sure is trivial.
I have a dictionary:
Dictionary<String^, Room^>^ roomList = gcnew Dictionary<String^, Room^>();
I'm trying to add a new Room to the dictionary:
Room r("Room 1", x, y);
roomList->Add(r.getName, %r);
Room is defined as follows:
ref class Room
{
private:
String^ mName;
double mX; //scaled X-coordinate of top left corner (meters)
double mY; //scaled Y-coordinate of top left corner (meters)
public:
Room(String^ name, double x, double y);
String ^ const getName() { return mName; }
double const getX() { return mX; }
double const getY() { return mY; }
};
When I try to compile the code I get the following error:
'Room::getName': non-standard syntax; use '&' to create a pointer to member"
What am I doing wrong? For some reason I can't use the object's name (a System::String^) as the key, but I'm not sure why.
roomList->Add(r.getName, %r);
You declared getName as a function, not a property. So it needs to be r.GetName(), note the added () parentheses. Declaring a Name property would be wise, it is the .NET way.
Room r("Room 1", x, y);
This declaration is technically wrong. You are using stack semantics, the r object will automatically be disposed when code execution leaves the scope block. You never want to add a disposed object to a collection. You'll get away with it in this case since you did not actually implement a destructor. Woe be you if you ever do. And woe the reader of your code. Just do it correctly:
Room^ r = gcnew Room("Room 1", x, y);
roomList->Add(r=>getName(), r);
Last but not least, this looks like a student assignment. You cannot get a passing grade for this code, it is not C++. The language you are using is called C++/CLI, it is an extension language that helps writing interop code for .NET programs.
I have the following code:
#include <iostream>
#include <utility>
#include <map>
using namespace std;
int main()
{
map<int, map<string, int> > mapa;
// way A
mapa[10]["aaa"] = 20;
// way B -> Compilation Error
pair<int, pair<string, int> > par(10, make_pair("aaa", 20));
mapa.insert(par);
return 0;
}
I know that "way A" of populating the map works.
I want to use "way B" but it throw a compilation Error:
error: no matching function for call to ‘std::map, int>::map(const std::pair, int>&)’
How can I populate the nested map with insert operator.
Pd: I don't use [] operator because it requires the default constructor to be defined which I don't have since I am using time_period objects from Boost.
Well the type of your map is map of (int -> map of (string -> int)) but you are trying to insert an entry of type map of (int -> pair (string, int)). A pair is not a map, thus the error.
EDIT:
According to the documentation, a call to map's [] operator is equivalent to a series of other operations:
mapped_type& operator[] (const key_type& k);
A call to this function is equivalent to:
(*((this->insert(make_pair(k,mapped_type()))).first)).second
so in your case, the call mapa[10]["aaa"] = 20; is equivalent to:
(*(( (*((mapa.insert(make_pair(10,map<string, int>()))).first)).second
.insert(make_pair("aaa",20))).first)).second
but I believe if either key 10 or aaa exist, no element will be inserted in the map. I suggest you read the docs thoroughly and test for the expected behavior.
I've got the following struct:
struct Param
{
double** K_RP;
};
And I wanna perform the following operations on "K_RP" in CUDA
__global__ void Test( struct Param prop)
{
int ix = threadIdx.x;
int iy = threadIdx.y;
prop.K_RP[ix][iy]=2.0;
}
If "prop" has the following form, how should I do my "cudaMalloc" and "cudaMemcpy" operations?
int main( )
{
Param prop;
Param cuda_prop;
prop.K_RP=alloc2D(Imax,Jmax);
//cudaMalloc cuda_prop ?
//cudaMemcpyH2D prop to cuda_prop ?
Test<<< (1,1), (Imax,Jmax)>>> ( cuda_prop);
//cudaMemcpyD2H cuda_prop to prop ?
return (0);
}
Questions like this get asked from time to time. If you search on the cuda tag, you'll find a variety of examples with answers. Here's one example.
In general, dynamically allocated data contained within structures or other objects requires special handling. This question/answer explains why and how to do it for the single pointer (*) case.
Handling double pointers (**) is difficult enough that most people would recommend "flattening" the storage so that it can be handled by reference with a single pointer (*). If you really want to see how the double pointer (**) method works, review this question/answer. It's not trivial.
(for the "D" programming language)
I've been struggling trying to initialise an associative array that has struct elements and should be index-able by a string. I would import it as a module from a separate file.
This is what I want to achieve (and it doesn't work --- I don't know if this is even possible):
mnemonic_info[string] mnemonic_table = [
/* name, format, opcode */
"ADD": {mnemonic_format.Format3M, 0x18},
...
/* NOTE: mnemonic_format is an enum type. */
/* mnemonic_info is a struct with a mnemonic_format and an ubyte */
];
Note that this works fine for arrays indexable by integers.
Optimally, I would like this to be evaluated at compile-time, as I won't be changing it. However, if it's not possible, I would be glad if you told me of the best way to build such an array at/before immediate run-time.
I need this because I'm writing an assembler.
I have searched SO and the internets for an answer, but could only find examples with integers, and other things I didn't understand or couldn't make to work.
I really like D so far but it seems hard to learn due to there not being many tutorials online.
Thanks!
On a side note: is it possible to use Tuples for associative array elements instead of a custom struct?
Edit
There is one way I found so far, but it's pretty ugly:
mnemonic_info[string] mnemonic_table;
static this() { // Not idea what this does.
mnemonic_info entry;
entry.format = mnemonic_format.Format3M;
entry.opcode = 0x18;
mnemonic_table["ADD"] = entry;
/* ... for all entries. */
}
In D, built-in associative array literals are always created in runtime, so initializing a global associative array by assigning it some value at declaration place is currently impossible.
As you found yourself, you can workaround that by assigning a value to associative array in module constructor.
The other problem in your code is struct initialization literals. You should prefer D-style struct initializers to C-style ones.
Example:
struct Foo {
int a;
string b;
}
Foo[string] global;
static this() {
global = [
"foo" : Foo(1, "hurr"),
"bar" : Foo(2, "durr")
];
}
void main() {
assert(global["foo"].a == 1);
}