Chapter 5 C++: Introduction to statements

Chapter 5 Statement

##Hanging else

refers to how to find the else when the if branch is hiding from the else branch Problem with the if branch that matches:

- C specifies that else matches the nearest if that hasn't been matched yet, thus removing the ambiguity.

switch

switch (ch) {    case 'a':    case 'b':
        ++n;        break;
}

• break jumps out of the switch control flow.

• case label (case label) must be

  integer constant expression.

• If a case label is matched successfully, all branches will be executed sequentially starting from the label. Unless the process is explicitly interrupted, it will not stop until the end of the switch. .

• Add curly braces ({ }) to the statement after the case tag to define the variable within the block, thereby ensuring that all subsequent case tags are outside the scope of the variable.

• default tag: a special case tag. When switch cannot match any case, the content under the default tag will be executed.

do while

do
    statementwhile (condition);  //注意分号

• Do not allow variables to be defined within loop conditions.

• And the variables in the conditional part must be defined outside the loop.

Jump statement

• break
  is responsible for terminating the while, do while, for or switch statement closest to it. And execution starts from the first statement after these statements.

• continue
  for, while, do while

##try statement block and exception handling

• throw expression

  (throw expression): The anomaly detection part uses throw expressions to indicate that it has encountered a problem that cannot be handled.
  

It is said that throw** raises an exception.
After an exception is thrown, the function will be terminated and control will be transferred to code that can handle the exception.

• try statement block

  （try block）：try starts with one or more catch clauses（catch clause） Finish.
  

#Exceptions thrown by the code in the try statement block are usually handled by a catch clause.
Call the catch clause
• as the exception handling code (exception handler)

  .

Exception class

• try {
      //program-statements
  } catch (/*exception-declaration异常声明*/) {
      //handler-statements
  } catch (/*exception-declaration*/) {
      //handler-statements
  } //...

  • Exception declaration

    Specify the Exception types that the catch clause can handle.

  Standard Exceptions

  C The standard library defines a set of classes for reporting problems encountered by standard library functions.

  In the following four header files:

  - exception: defines the most common exception class exception, which only reports the occurrence of exceptions and does not provide any additional information.
  - stdexcept
  - Use string objects or C-style string initialization
  - There is only one member function what()
  
  
  Exception //The most common problems runtime_error //Problems that can only be detected at runtime <br> overflow_error // <br> Underflow_error <br> Logic_error <br> domain_error <br> invalid_arguement <br> length_error <br> out_og_range <br><br> <br>- new: bad_alloc - type_info: bad_cast
  
  Reference: C Primer 5th Edition

  Related articles:

  Chapter 4 C: Expression Concept - Application of Operators
  Chapter 6 C: Function Basics and Application

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