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1. Top results related to switch case c++ syntax

   • Switch Case in c++

     Top Answer

     Answered May 23, 2013 · 10 votes

     If you really need a switch statement, you will need to convert your buff variable to an integer. To do so, you could use a hash function or a std::map.

     The easy approach would be to make a std::map<std::string,int> containing the keys you want to use in the switch associated with unique int values. You would get something like:

     std::map<string,int> switchmap;...switch(switchmap.find(std::string(buff))->second){...}

     The std::map approach is very readable and shouldn't cause much confusion.

     Other Answers

     Answered May 23, 2013 · 3 votes

     You just can't use an array as the expression in a switch construct.

     Other Answers

     Answered May 23, 2017 · 3 votes

     In C++ case statements require a constant integer value and cannot be used with values calculated at runtime. However if you are using C++11 you can use a constexpr function to generate case values simulate using strings with a case statement.

     This uses a hash function that takes a pointer to a string and generates a value at compile time instead of runtime. If more than one string generates the same value (a hash collision) you get the familiar error message about multiple case statements using the same value.

     constexpr unsigned int djb2Hash(const char* str, int index = 0){ return !str[index] ? 0x1505 : (djb2Hash(str, index + 1) * 0x21) ^ str[index];}

     The djb2Hash function can then be used directly in both the switch and case statements. There is one caveat however, the hash function can result in a collision at runtime. The probability of this happening is driven primarily by the quality of the hash function. The solution presented here does not attempt to address this problem (but may in the future).

     void DoSomething(const char *str){ switch(djb2Hash(str)) { case djb2Hash("Hello"): SayHello(); break; case djb2Hash("World"): SayWorld(); break; }}

     This works very well but might be considered ugly. You can simplify this further by declaring a user defined literal that handles invoking the hash function.

     // Create a literal type for short-hand case stringsconstexpr unsigned int operator"" _C ( const char str[], size_t size){ return djb2Hash(str);}void DoSomething(const char *str){ switch(djb2Hash(str)) { case "Hello"_C: SayHello(); break; case "World"_C: SayWorld(); break; }}

     This provides a more intuitive usage of strings in a switch statements but may also be considered slightly confusing because of the user defined literal.

     [Edit: Added note about runtime hash collisions. Much Kudos to R. Martinho Fernandes for bringing it to my attention!]

     Check all answers on Stack Overflow

     1/5

   • Switch Case Statement C++ Coding Style

     Top Answer

     Answered Jan 10, 2014 · 2 votes

     I agree, that this is a personal matter, but I believe, that first option is the most readable.

     I'm also using it in situations, when function should react for some values, but also explicitly shouldn't react for others:

     switch(o.fruitType){ case APPLE: { DoSomethingWithApple(); break; } case PEAR: { DoSomethingWithPear(); break; } case ORANGE: { DoSomethingWithOrange(); break; } default: { // Explicitly left empty }}

     I leave this "Explicitly left empty" comment, such that future readers of my code will know, that I explicitly wanted that piece of code to do nothing if other value is encountered. And optimizer will cut this code out, so it won't affect performance.

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     2/5

   • C/C++ switch case with string

     Top Answer

     Answered Dec 18, 2010 · 39 votes

     Just use a if() { } else if () { } chain. Using a hash value is going to be a maintenance nightmare. switch is intended to be a low-level statement which would not be appropriate for string comparisons.

     Other Answers

     Answered May 23, 2013 · 3 votes

     You just can't use an array as the expression in a switch construct.

     Other Answers

     Answered May 23, 2017 · 3 votes

     In C++ case statements require a constant integer value and cannot be used with values calculated at runtime. However if you are using C++11 you can use a constexpr function to generate case values simulate using strings with a case statement.

     This uses a hash function that takes a pointer to a string and generates a value at compile time instead of runtime. If more than one string generates the same value (a hash collision) you get the familiar error message about multiple case statements using the same value.

     constexpr unsigned int djb2Hash(const char* str, int index = 0){ return !str[index] ? 0x1505 : (djb2Hash(str, index + 1) * 0x21) ^ str[index];}

     The djb2Hash function can then be used directly in both the switch and case statements. There is one caveat however, the hash function can result in a collision at runtime. The probability of this happening is driven primarily by the quality of the hash function. The solution presented here does not attempt to address this problem (but may in the future).

     void DoSomething(const char *str){ switch(djb2Hash(str)) { case djb2Hash("Hello"): SayHello(); break; case djb2Hash("World"): SayWorld(); break; }}

     This works very well but might be considered ugly. You can simplify this further by declaring a user defined literal that handles invoking the hash function.

     // Create a literal type for short-hand case stringsconstexpr unsigned int operator"" _C ( const char str[], size_t size){ return djb2Hash(str);}void DoSomething(const char *str){ switch(djb2Hash(str)) { case "Hello"_C: SayHello(); break; case "World"_C: SayWorld(); break; }}

     This provides a more intuitive usage of strings in a switch statements but may also be considered slightly confusing because of the user defined literal.

     [Edit: Added note about runtime hash collisions. Much Kudos to R. Martinho Fernandes for bringing it to my attention!]

     Check all answers on Stack Overflow

     3/5

   • switch case with string in c++

     Top Answer

     Answered Nov 14, 2014 · 2 votes

     Don't fight the language. You can't switch on strings in C++ as you know.

     Use if, else if instead.

     You do see various attempts crop up from time to time. Maps, enums, and hashes being three I can think of. But they just obfuscate. And you'll probably need break statements which worsen things further. (If follow through would have been useful then structure the equivalent if block accordingly).

     Your ; error is due to string enum being syntatically invalid.

     Check all answers on Stack Overflow

     4/5

   • Switch Case and For Loop C++

     Top Answer

     Answered Apr 27, 2014 · 3 votes

     switch (coursepick){case 1: course= "Maths"; break;case 2: course= "Quantum"; break;case 3: course= "Reality"; break;default: break;}

     if you don't break at the end of each case, it just continue with the next, and the next, and then until case 3 and break on default.

     Check all answers on Stack Overflow

     5/5

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2. www.programiz.com › cpp-programming › switch-caseC++ switch...case Statement (With Examples) - Programiz

   www.programiz.com › cpp-programming › switch-case

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   C++ switch..case Statement. The switch statement allows us to execute a block of code among many alternatives. You can do the same thing with the if...else statement. However, the syntax of the switch statement is much easier to read and write. Syntax. switch (expression) { case constant1:

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3. en.cppreference.com › w › cppswitch statement - cppreference.com

   en.cppreference.com › w › cpp

   • Cached

   • Condition
   • Labels
   • Control Flow Transfer
   • Notes
   • Defect Reports

   A condition can either be an expression or a simple declaration. If it can be syntactically resolved as either an expression or a declaration, it is interpreted as the latter. When control reaches condition, the condition will yield a value, which is used to determine which label the control will go to.

   See full list on en.cppreference.com

   Any statement within the switchstatement can be labeled with one or more following labels: A case or default label is associated with the innermost switchstatement enclosing it. If any of the following conditions is satisfied, the program is ill-formed: 1. A switch statement is associated with multiple case labels whose constant-expressions have t...

   See full list on en.cppreference.com

   When the condition of a switchstatement yields a (possibly converted) value: 1. If one of the associated case label constants has the same value, control is passed to the statement labeled by the matched caselabel. 2. Otherwise, if there is an associated default label, control is passed to the statement labeled by the defaultlabel. 3. Otherwise, no...

   See full list on en.cppreference.com

   Because transfer of control is not permitted to enter the scope of a variable, if a declaration statement is encountered inside the statement, it has to be scoped in its own compound statement:

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   The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

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4. www.geeksforgeeks.org › switch-statement-in-cppSwitch Statement in C++ - GeeksforGeeks

   www.geeksforgeeks.org › switch-statement-in-cpp

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   Apr 17, 2024 · Syntax of switch Statement in C++. switch (expression) { case value_1: // statements_1; . break; case value_2: // statements_2; . break; ..... default: // default_statements; . break; } The following example demonstrate how to use the switch statement syntax in C++. Example: C Program to demonstrate the syntax of switch in C++. C++.

   • Video Duration: 2 min

5. www.w3schools.com › cpp › cpp_switchC++ Switch - W3Schools

   www.w3schools.com › cpp › cpp_switch

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   C++ Switch Statements. Use the switch statement to select one of many code blocks to be executed. Syntax. switch(expression) { case x: // code block. break; case y: // code block. break; default: // code block. } This is how it works: The switch expression is evaluated once. The value of the expression is compared with the values of each case.

6. www.programmingsimplified.org › switch-caseC++ switch...case Statement (With Examples)

   www.programmingsimplified.org › switch-case

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   The syntax of the switch statement in C++ is: switch (expression) {. case constant1: // code to be executed if. // expression is equal to constant1; break; case constant2: // code to be executed if. // expression is equal to constant2;

7. www.guru99.com › cpp-switch-exampleC++ Switch Case Statement with Program EXAMPLES - Guru99

   www.guru99.com › cpp-switch-example

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   Feb 24, 2024 · Here is the syntax for switch statement: switch (variable) { case 1: break; case 2: break; default: } The above parameters are explained below: Variable: This is the variable for which comparison is to be made. Case: There are many case statements. Each compares the variable with a different value.

8. People also ask

   What is the syntax of a switch case in C?

   • A general syntax of how switch-case is implemented in a ‘C’ program is as follows: switch ( expression ) { case value-1: Block-1; Break; case value-2: Block-2; Break; case value-n: Block-n; Break; default: Block-1; Break; } Statement-x; The expression can be integer expression or a character expression.

   switch…case in C (Switch Statement in C) with Examples - Guru99

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   What is the difference between a switch case and an if else statement in C?

   • The switch statement in C is an alternative to the if-else-if ladder statement which allows us to execute multiple operations for the different possibles values of a single variable called the switch variable.

   C - Switch Statement - GeeksforGeeks

   www.geeksforgeeks.org/c-switch-statement/

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   How do you use switch case in c?

   • When working with switch case in C, you group multiple cases with unique labels. You need to introduce a break statement in each case to branch at the end of a switch statement. The optional default case runs when no other matches are made. Four, Five, or Six. In C, we can have an inner switch embedded in an outer switch.

   switch…case in C (Switch Statement in C) with Examples - Guru99

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   What is the syntax for a switch statement in C?

   • The syntax for a switch statement in C programming language is as follows − switch (expression) { case constant-expression : statement (s); break; /* optional */ case constant-expression : statement (s); break; /* optional */ /* you can have any number of case statements */ default : /* Optional */ statement (s); }

   Switch case statement in C - tutorialspoint.com

   www.tutorialspoint.com/switch-case-statement-in-c

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9. learn.microsoft.com › en-us › cppswitch statement (C++) | Microsoft Learn

   learn.microsoft.com › en-us › cpp

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   Jan 24, 2023 · A switch statement causes control to transfer to one labeled-statement in its statement body, depending on the value of condition. The condition must have an integral type, or be a class type that has an unambiguous conversion to integral type.