D Programming Exception Handling - D Programming Language

What is D Programming Exception Handling?

An exception is a problem that arises throughout the execution of a program. A D exception is a reply to an exceptional circumstance that arises while a program is running, such as an attempt to divide by zero.

Exceptions offer a way to transfer control from one part of a program to another. D exception handling is built upon three keywords try, catch, and throw.

  • throw − A program throws an exception when a problem shows up. This is done using a throw keyword.
  • catch − A program catches an exception with an exception handler at the place in a program where you want to handle the problem. The catch keyword indicates the catching of an exception.
  • try − A try block identifies a block of code for which particular exceptions are activated. It is followed by one or more catch blocks.

Assuming a block will enhance an exception, a method catches an exception using a combination of the try and catch keywords. A try/catch block is positioned across the code that might generate an exception. Code inside a try/catch block is called protected code, and the syntax for using try/catch looks like the following –

You can list down multiple catch statements to catch different type of exceptions in case your try block raises more than one exception in different situations.

Throwing Exceptions in D

Exceptions can be thrown anywhere within a code block using throw statements. The operand of the throw statements determines a type for the exception and can be any expression and the type of the result of the expression determines the type of exception thrown.

The following example throws an exception when dividing by zero condition occurs −

Example

Catching Exceptions in D

The catch block following the try block catches any exception. You can specify what type of exception you want to catch and this is determined by the exception declaration that appears in parentheses following the keyword catch.

The above code catches an exception of ExceptionName type. If you want to specify that a catch block should handle any type of exception that is thrown in a try block, you must put an ellipsis,..., between the parentheses enclosing the exception declaration as follows −

The following example throws a division by zero exception. It is caught in catch block.

When the above code is compiled and executed, it reads the file created in previous section and produces the following result −

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