The following breaks on the last line of main():
import std.stdio, std.traits;
void main(){
void test(ref int){}
void delegate(Parameters!test) works = &test;
template broken(Args...){
void delegate(Args) broken;
}
broken!(Parameters!test) = &test; // Error: cannot implicitly convert expression &test of type void delegate(ref int _param_0) pure nothrow #nogc #safe to void delegate(int)
}
Is this intended? If so, how to work around it?
Related
So this is a new one for me. When I try to compare 2 integers, the error tells me that Int should be Void -> Int, which is something I have never even seen before.
The code:
public static function whenTouchEnds(event:TouchEvent){
for (item in currentTouches){
if (item.getId == event.touchPointID){
currentTouches.remove(item);
trace("removed touch");
break;
}
}
}
Following the Haxe documentation, I also tried:
public static function whenTouchEnds(event:TouchEvent){
for (item in currentTouches){
if (item.getId == event.touchPointID) break;
}
}
And for the sake of trail and error (hobby programmer here) even tried:
public static function whenTouchEnds(event:TouchEvent){
for (item in currentTouches){
var itemID:Int = item.getId;
var touchID:Int = event.touchPointID;
if (itemID == touchID){
currentTouches.remove(item);
trace("removed touch");
break;
}
}
}
They all gave me the same error message "Int should be Void -> Int". Here is the Touch class I created which returns an Integer with the getId function:
class Touch
{
public var id:Int = 0;
public var xPos:Int = 0;
public var yPos:Int = 0;
public function new(Id:Int, X:Int, Y:Int)
{
id = Id;
xPos = X;
yPos = Y;
}
public function getX() : Int
{
return (xPos);
}
public function getY() : Int
{
return (yPos);
}
public function getId() : Int
{
return (id);
}
}
I'm not looking for a simple solution, but rather an explanation of what I am missing here. The more I learn, the better!
Cheers
The culprit is this line:
if (item.getId == event.touchPointID)
Since there's no parentheses, you're not actually calling the getId() function here - you're comparing it to an integer (which doesn't make sense). Try this instead:
if (item.getId() == event.touchPointID)
Void -> Int is Haxe's notation for a function type, specifically a function that takes no parameters (Void) and returns an integer. You're comparing such a function to an Int, hence the error message "Int should be Void -> Int".
A small code style critique: the get* functions in your Touch class don't really seem to serve any purpose, the variables are public anyway. If you ever want to do something more complex than just returning the variable in a getter function, you might want to look into using properties instead.
I am trying to pass a struct as a compile time argument to a function.
I think the code is self explanatory. I am fairly certain that this should work. But I don't know why it won't work.
void main(string[] args)
{
const FooStruct fooStruct = FooStruct(5);
barFunction!fooStruct();
}
public struct FooStruct()
{
private const int value_;
#property int value() { return value_; }
this(int value) const
{
value_ = value;
}
}
public static void barFunction(FooStruct fooStruct)
{
fooStruct.value; /// do something with it.
}
public struct FooStruct()
Here, you're declaring FooStruct to be a templated struct, with no variables. If that's what you want, you'll need to refer to FooStruct!() on this line:
public static void barFunction(FooStruct fooStruct)
Since FooStruct takes no template arguments, there's not really any need for it to be templated, and you should probably declare it like this:
public struct FooStruct
When you do that, the error message changes to constructor FooStruct.this (int value) const is not callable using argument types (int). That's because you're invoking the mutable constructor. To fix that, change line 3 to read const FooStruct fooStruct =constFooStruct(5);.
Finally, when you call barFunction, you are attempting to pass fooStruct as a template parameter (barFunction!fooStruct()). Since barFunction is not a templated function, this fails. You probably meant barFunction(fooStruct).
I can't seem to make this work let alone compile and I am at loss at how to fix it. My teacher gave us the following code (simplified for question's sake):
public static void doing1(String s) {
// add code here
}
public static void doing2(char start, char end) {
// add code here
}
public static int doing3(int num) {
// add code here
}
public static void doing4(Scanner keyboard) {
// add code here
}
I know what needs to go in each method (the work I mean) I just don't know how to print it out in the main method. We cannot change the code given to us, only add to it.
Thank you!
Overloading a method means having the same method name but the method signature (the parameters passed in) is different. So, what you have isn't actually an overload, it is for unique methods because they all have different names. As far as not compiling... what you posted looks fine - perhaps you have an error above or below that code. I believe this is what you are looking for:
public static void doing(String s) {
// add code here
}
public static void doing(char start, char end) {
// add code here
}
public static int doing(int num) {
// add code here
}
public static void doing(Scanner keyboard) {
// add code here
}
Here's a reference on overloads from the almighty John Skeet
Here is my header file in Visual C++ Express 2010 (note the last line):
/* custom class header to communicate with LynxMotion robot arm */
using namespace System;
using namespace System::IO::Ports;
public ref class LynxRobotArm
{
public:
LynxRobotArm();
~LynxRobotArm();
void connectToSerialPort(String^ portName, int baudRate);
void disconnectFromSerialPort();
void setCurrentPosition(int channel, int position);
int getCurrentPosition(int channel);
void moveToPosition(int channel, int position);
private:
void initConnection();
SerialPort^ serialPort;
array<String^> ^serialPortNames;
String^ portName;
int baudRate;
std::vector<int> *currentPosition;
};
I try to assign a value to the vector by using this function;
void LynxRobotArm::setCurrentPosition(int channel, int position)
{
currentPosition[channel] = position;
}
The compiler gives me an error C2679:
binary '=' : no operator found which takes a right-hand operand of type 'int' (or there is no acceptable conversion)
I looked up at MSDN and they say:
To use the operator, you must overload it for the specified type or define a conversion to a type for which the operator is defined.
I tried using currentPosition.at(channel) = position but it did not make a difference.
I am stuck... quite new to pointers, noted that using std::vector<int> currentPosition; instead of std::vector<int> *currentPosition; does not compile.
How should my set-function work? (will try getter afterwards..)
I was just trying to code the following extension method:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace _4Testing
{
static class ExtensionMethods
{
public static void AssignMe(this int me, int value)
{
me = value;
}
}
}
But it is not working, i mean, can I use an extension method to alter values from extended classes? I don't want to change void return type to int, just changing extended class value. Thanks in advance
Your example uses int, which is a value type. Classes are reference types and behaves a bit differently in this case.
While you could make a method that takes another reference like AssignMe(this MyClass me, MyClass other), the method would work on a copy of the reference, so if you assign other to me it would only affect the local copy of the reference.
Also, keep in mind that extension methods are just static methods in disguise. I.e. they can only access public members of the extended types.
public sealed class Foo {
public int PublicValue;
private int PrivateValue;
}
public static class FooExtensions {
public static void Bar(this Foo f) {
f.PublicValue = 42;
// Doesn't compile as the extension method doesn't have access to Foo's internals
f.PrivateValue = 42;
}
}
// a work around for extension to a wrapping reference type is following ....
using System;
static class Program
{
static void Main(string[] args)
{
var me = new Integer { value = 5 };
int y = 2;
me.AssignMe(y);
Console.WriteLine(me); // prints 2
Console.ReadLine();
}
public static void AssignMe(this Integer me, int value)
{
me.value = value;
}
}
class Integer
{
public int value { get; set; }
public Integer()
{
value = 0;
}
public override string ToString()
{
return value.ToString();
}
}
Ramon what you really need is a ref modifier on the first (i.e. int me ) parameter of the extension method, but C# does not allow ref modifier on parameters having 'this' modifiers.
[Update]
No workaround should be possible for your particular case of an extension method for a value type. Here is the "reductio ad absurdum" that you are asking for if you are allowed to do what you want to do; consider the C# statement:
5.AssignMe(10);
... now what on earth do you think its suppose to do ? Are you trying to assign 10 to 5 ??
Operator overloading cannot help you either.
This is an old post but I ran into a similar problem trying to implement an extender for the String class.
My original code was this:
public static void Revert(this string s)
{
char[] xc = s.ToCharArray();
s = new string(xc.Reverse());
}
By using the new keyword I am creating a new object and since s is not passed by reference it will not be modified.
I changed it to the following which provides a solution to Ramon's problem:
public static string Reverse(this string s)
{
char[] xc = s.ToCharArray();
Array.Reverse(xc);
return new string(xc);
}
In which case the calling code will be:
s = s.Reverse();
To manipulate integers you can do something like:
public static int Increment(this int i)
{
return i++;
}
i = i.Increment();