c++ cannot assign to a variable that is const
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const (C++) The const keyword specifies that a variable's value is constant and tells the compiler to prevent the programmer from modifying it. In C++, you can use the const keyword instead of the #define preprocessor directive to define constant values. Values defined with const are subject to type checking, and can be used in place of constant expressions. In C++, you can specify the size of an array with a const variable as follows: Copy.
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Determining length of a char* string in C++ Note: cost always binds to the type on its left. unless it is the left-most part of a type declaration then it binds right. Read type right to left. Basically str1 and str3 are identical. But the consistency of always thinking that const binds to the left makes it neater in my mind.
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The Role of Independent Investment Company Directors - Part 2 Reading lines from a text file and assigning different variables in c++. up vote -1 down vote favorite. I'm working on an address book application, and the portion I'm really struggling with is getting text from a .txt file and assigning the correct variable to each piece of text. each piece is delineated with a tab.I'm really struggling with this one.DIT** the text file goes something like this. so on and so forth. What I need to do is read through the text file and fill the array elements for each attribute (first, last, month, day, year, address, city, state, zip, phone).
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- There are however a few issues: 1  When compiling C or C++, use the -D_REENTRANT define in the compiler command line. 2  When using C++, If two threads throw exceptions concurrently, the program will segfault.
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Variables and Constants in C++ When you define a variable in C++, you must tell the compiler not only what its name is, but also what kind of information it will hold: integer, character, and so forth. This is the variable's type. The type of the variable tells the compiler how much room to set aside in memory to hold the variable's value. Each cubby is one byte large. If the type of variable you create is two bytes in size, it needs two bytes of memory, or two cubbies. The type of the variable (for example, int) tells the compiler how much memory (how many cubby holes) to set aside for the variable.
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Storage classes (C++) Objects and variables declared as extern declare an object that is defined in another translation unit or in an enclosing scope as having external linkage. Declaration of const variables with the extern storage class forces the variable to have external linkage.
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- Do the following changes in your Turbo C/C++ code: 1  For C++ code, remove “.h” from the header files. 2  If writing in C++, add “using namespace std” after the header files. 3  Instead of “void main()”, write “int main (void)”. 4  Don’t use outdated header files like <conio. h>.
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- up vote 83 down vote accepted. This is C++/CLI and the caret is the managed equivalent of a * (pointer) which in C++/CLI terminology is called a 'handle' to a 'reference type' (since you can still have unmanaged pointers).(Thanks to Aardvark for pointing out the better terminology.). share | improve this answer. edited Mar 15 '10 at 11:47.his is C++/CLI and the caret is the managed equivalent of a * (pointer) which in C++/CLI terminology is called a 'handle' to a 'reference type' (since you can still have unmanaged pointers). (Thanks to Aardvark for pointing out the better terminology.). share | improve this answer. edited Mar 15 '10 at 11:47.
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Storage classes (C++) In C++11, the register keyword is deprecated. It specifies that the variable is to be stored in a machine register, if possible. Only function arguments and local variables can be declared with the register storage class.
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Is there an appropriate use for #define for constants? In C, you often have to use #define. In C++, you can avoid it. The problem with #define is that it's a textual substitution that has file scope. It's not possible to limit its scope. If you want two different #defines for different parts of the program, you can't put them in different namespaces.
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What does dereferencing mean in C & C++ programming? In C++, you can bind an lvalue reference to the object identity obtained by dereferencing, so if you don't want to think in terms of lvalues, a useful mental model, in my opinion, is that dereferencing a pointer obtains a reference to the pointed-to object: int& r = *p; // deref, then associate a new name.
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const The constant's name, which can be any legal identifier. valueN. The constant's value; this can be any legal expression. This declaration creates a constant that can be either global or local to the function in which it is declared. An initializer for a constant is required; that is, you must specify its value in the same statement in which it's declared (which makes sense, given that it can't be changed later). The const declaration creates a read-only reference to a value.
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- A pointer to a function must specify whether it points to a C function or to a C++ function, because it is possible that C and C++ functions use different calling conventions. Otherwise, the compiler does not know which kind of function-calling code to generate.
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"What does ""const string&"" in C++ mean?" f(const string&) takes string by const reference: f is operating directly on the string object passed by reference: there is no copy involved. const prevents modifications to the original object though. f(const string) takes a string value, which means f is given a copy of the original string. Even if you drop const, when passing by value, any modification to the string is lost when f returns. It passes value by a read only reference.
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Storage classes (C++) Objects and variables declared as extern declare an object that is defined in another translation unit or in an enclosing scope as having external linkage. Declaration of const variables with the extern storage class forces the variable to have external linkage. An initialization of an extern const variable is allowed in the defining translation unit. Initializations in translation units other than the defining translation unit produce undefined results.
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switch Statement (C++) None of the constants match the constants in the case labels; a default label is present. Control is transferred to the default label. None of the constants match the constants in the case labels; default label is not present. Control is transferred to the statement after the switch statement. If a matching expression is found, control is not impeded by subsequent case or default labels.
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Function Overloading Although functions can be distinguished on the basis of return type, they cannot be overloaded on this basis. Const or volatile are only used as a basis for overloading if they are used in a class to apply to the this pointer for the class, not the function's return type.
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Best 15 Foods to cleanse your Lungs Best food to cleanse your lungs in a natural way: 1  1. Garlic – garlic has various anti-inflammatory properties along with a high level of allicin. 2  3. Turmeric – just like ginger and garlic, this spice is great for your lungs due to its anti-inflammatory properties.
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Creating Variables and Constants in C++ You can't assign a value to 5, and its value can't be changed. The values true and false, which are stored in bool variables, also are literal constants. A symbolic constant is a constant represented by a name, just like a variable. The const keyword precedes the type, name, and initialization.
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- Report Abuse. a const variable is constant and cannot be altered. A static variable is stored on the heap rather than on the call stack so it is accessible outside of the current scope and therefore can be shared between different processes. gitter1226 · 8 years ago.
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- // using #include <iostream> using namespace std; namespace first { int x = 5; int y = 10; } namespace second { double x = 3.1416; double y = 2.7183; } int main () { using namespace first; cout << x << ; cout << y << ; cout << second::x << ; cout << second::y << ; return 0; }.
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Structures in C++ struct Person is a datatype and can be used in exactly the same way as we use int, float, or other C++ datatypes. struct Person is not a variable name and to use a struct you must first define variables of that type. This can be done in two ways. When you originally define a struct you can define a variable or variables. In the definition above, tom is the name of a variable of type struct Person. We could declare more than one variable this way.
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- up vote 5 down vote. You can template a struct as well as a class. However you can't template a typedef. So works, but does not. Note that there is no need for the typedef trick in C++ (you can use structs without the struct modifier just fine in C++).share | improve this answer.n a template-declaration, explicit specialization, or explicit instantiation the init-declarator-list in the dec-laration shall contain at most one declarator. When such a declaration is used to declare a class template, no declarator is permitted. The Standard says (at 14/3.
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- i need to share some strings in my c++ program. should i use #define or const string? thanks. mystring1.h . #define str1 str1 #define str2 str2 Or mystring2.h . extern const string str1; extern const string str2; mystring.cpp . const string str1 = str1; const string str2 = str2;
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Static (C++) Static (C++) The static keyword can be used to declare variables, functions, class data members and class functions. By default, an object or variable that is defined outside all blocks has static duration and external linkage. Static duration means that the object or variable is allocated when the program starts and is deallocated when the program ends.
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- #include <iostream> using namespace std; int const k=2; // the number of dimensions double min_distance = 10000; // set a large default value, in this example all distance will be shorter than this.