Recover in D Programming Language

D makes it possible to recover from an error, by using the try-catch mechanism. A catch block can stop an exception from aborting the program and let it continue with execution instead.

An example of where this can be useful: a server wouldn’t want to crash if one of the client connections exhibits a critical error. Instead, the server would want to close that connection and continue serving other clients.

import std.stdio;

// This function throws an exception.
void mayThrow()
{
    throw new Exception("a problem");
}

void main()
{
    try
    {
        // The catch block will handle any exceptions thrown in this try block.
        mayThrow();

        // This code will not run, because mayThrow throws an exception.
        // The execution of main stops at the point of the exception
        // and resumes in the catch block.
        writeln("After mayThrow()");
    }
    catch (Exception e)
    {
        // The catch block is equivalent to the deferred function in the original example.
        // The caught exception is the error raised in the call to mayThrow.
        writeln("Caught. Error:\n", e.msg);
    }
}

To run the program, save it as recover.d and use the D compiler:

$ dmd recover.d
$ ./recover
Caught. Error:
a problem

In D, we use try-catch blocks to handle exceptions, which is similar to recovering from panics in other languages. The catch block catches any exceptions thrown in the try block, allowing the program to continue execution rather than crashing.

The main difference from some other languages is that D uses exceptions for error handling, which are more structured and provide more information than simple panics. This allows for more fine-grained error handling and recovery.