In this group, who are the experts or teachers of c programming, whoever they are, raise your hand or type yes and send it. I am creating a group .. I add to it .. I need help for the exam ..

Please I just want to start

Please I just want to start

why some libs has implemented as *.hpp files, not a *.h and *.cpp like classic c++

https://github.com/Snowapril/String-Obfuscator-In-Compile-Time

this is an example of metaprograming. I think the *.hpp using if *.cpp is not needs and the functions or classes are not implemented at all

ok *.h = *.hpp at c++. But where is *.cpp ? Is it really not needed if library used only macroses and only templates?

why some libs has implemented as *.hpp files, not a *.h and *.cpp like classic c++

Header only libraries are used only when the libraries are small and also when there is template metaprogramming involved. Header only libraries have the advantage of making the build process easier. You dont need to link your libraries in. Just including the header file is good enough. If bigger libraries are implemented as header only libraries it will lead to problems like hugely increased translation unit and object file sizes (in other words code bloat) and will also increase the build time of your code. If you make changes to a header only library you will have to recompile all the source files that include the header files. In a normal library (with both .hpp and .cpp files), you will need to build the client code only if the header file changes. Otherwise, just linking again is good enough. The client code does not need to be recompiled. So, only small libraries like the individual units in Boost and others are implemented as header only libraries. Bigger projects need to separate the interfaces and the implementation.

Any one tell us how to work reflection in java

This is a C/C++ community but since Reflection is being considered for the C++26 standard, I will tell you how it works in Java. Java compiles its code to byte code. While doing it, Java compiler generates a lot of support classes when it compiles your class. These support classes actually help you with reflection support but it is considered to be very slow because reflection queries involve a lot of pointer indirection and string comparisons which all add to overhead at runtime. For ex Java compiler when it is compiling class A will create a helper class MethodsA (not the actual name) which will use something like a hash map which maps the function names and their parameters to a pointer to this method. So when you query a class object at runtime for its methods, the Java compiler will generate the byte codes to call the methods in MethodA class instead. (To be accurate, this is not exactly the case. Actually there are multiple calls made through a hierarchy of classes with A.class (not the same as the class bytecode file generated by javac when it compiles A.java) being the top class). What I have summarized here is just a simplification. But the overall idea is the same.

eg this CANNOT be in a header only file class HEADER_ONLY_MATH { // WRONG, this will produce duplicate definition HEADER_ONLY_MATH::sum void sum(int a, int b) { return a + b; } // CORRECT, this will NOT produce duplicate definition due to template instantiation template <typename T> void sum_(T a, T b) { return a + b; } } // CORRECT, this will NOT produce duplicate definition due to template instantiation template <typename T> class HEADER_ONLY_MATH_TEMPLATE { void sum(T a, T b) { return a + b; } }

You can use the first part (before the switch structure) of main function like this 👇 WITHOUT using ctype.h I mentioned. float num1,num2,result; int choice = 0; int err; do { printf("1.Addition\n"); printf("2.Subtraction\n"); printf("3.Multiplication\n"); printf("4.Division\n"); printf("5.Exit\n\n"); do{ printf("Enter Your Choice : "); err = scanf("%d",&choice); getchar(); if(err != 1) puts("Your choice must be an integer!"); } while(err != 1);

How if i when i enter for num1,i want it print out your choice must be an integer,when i enter letter

Oh, it can't catch up C++23?

tho i am not sure if using TEMPLATE<int> in multiple translation units will produce multiple definitions of class TEMPLATE since they both instantiate to the exact same type

Hello, good morning. Does anyone know c ++ language? I have a few coding questions

Hello, good morning. Does anyone know c ++ language? I have a few coding questions

I am a student and I have a C ++ exam. Can anyone help me?

Just ask your question, someone will help

I am a student and I have a C ++ exam. Can anyone help me?

The exam starts in another hour

Hi

How if i when i enter for num1,i want it print out your choice must be an integer,when i enter letter

Depends on how your class template is defined. Class template instantiations in header only libraries should not violate ODR rules.

Hmm even if, say template <typename T> class X { T add(T a, T b) { return a + b; } } A.cpp X<int> x; B.cpp X<int> X;

tho i am not sure if using TEMPLATE<int> in multiple translation units will produce multiple definitions of class TEMPLATE since they both instantiate to the exact same type

Hmm even if, say template <typename T> class X { T add(T a, T b) { return a + b; } } A.cpp X<int> x; B.cpp X<int> X;

move template to *.hpp and reinclude at *.cpp files

This doesnt violate ODR. The method "add" is inline here and the linker folds multiple such instantiations into a single one.

C++ has static storage class of global variables by default

#pragma once

In c++ if I create an array of size 10 and I want to access 10th index then why compiler gives no error. Int a(10); Cout<<a(10)

In c++ if I create an array of size 10 and I want to access 10th index then why compiler gives no error. Int a(10); Cout<<a(10)

You are accessing something that neither exists

I know but my question is compiler doesn't stop me from doing so.

In c++ if I create an array of size 10 and I want to access 10th index then why compiler gives no error. Int a(10); Cout<<a(10)

I know but my question is compiler doesn't stop me from doing so.

Because the standards dont require them to. But most compilers do warn about it. And the reason why the standards dont require a diagnostic is because it is impossible for the compilers to determine all contexts where an out of bounds indexing happens. So the standards cant be restrictive and say that this diagnostic is required only in the cases where a constexpr index is used.

What is constexpr idx. And what is sigsev?

In c++ if I create an array of size 10 and I want to access 10th index then why compiler gives no error. Int a(10); Cout<<a(10)

I was trying to implement segmented sieve but when I compile (on codechef ide)I get an error SIGSEV. And I can't find the reason why?? Can I share the whole code here

In c++ if I create an array of size 10 and I want to access 10th index then why compiler gives no error. Int a(10); Cout<<a(10)

This is runtime information the compiler doesn't check for that, you can use a.at(10); then it will throw an exception

Debug it. It usually happens when you access memory that you are not supposed to. People here may not do the debugging for you.

As you said compiler doesn't throw an error even if I try to access out of bounds of array then why am I getting SIGSEV

As you said compiler doesn't throw an error even if I try to access out of bounds of array then why am I getting SIGSEV

When you say "compiler" do you mean that it should happen on compile time?

Because C++ compilers are not required to determine if your program can access memory it is not supposed to. And so if you do so, the compiler happily generates the machine code that does so. But your OS is an asshole and wouldnt let you off so easily.

Yea

I still can't find why am I getting a seg fault. I have tried to debug it. Can anyone help