• Patrick Down <pat codemoon.com> Jul 31 2002
• Burton Radons <loth users.sourceforge.net> Jul 31 2002
• Pavel Minayev <evilone omen.ru> Jul 31 2002

Patrick Down <pat codemoon.com> writes:

I'm a little surprised that this does not throw
an error.  It prints a = 0.  When an assocative array
doesn't have a key does it return the type.init
value?

int main(char[][] args)
{
  int[char[]] intmap;
  
  int a = intmap["betty"];
  
  printf("a = %d\n",a);

  return 0;
}

Burton Radons <loth users.sourceforge.net> writes:

Patrick Down wrote:

 I'm a little surprised that this does not throw
 an error.  It prints a = 0.  When an assocative array
 doesn't have a key does it return the type.init
 value?



Yup.  You can use the "in" operator to make the check yourself.

I see the reasons as being:

- Exceptions are far more expensive than normal execution, so 
exception-dependent operations are avoided.

- Most language-based exceptions should be turned off when all debugging 
is killed, but this would alter normal execution here.

- It's often convenient.  If you're treating it as a set, for example, 
then just normal testing tells you whether an object is included in it. 
  For objects, you can get the in and the what at the same time without 
having to build a try/catch around it.

But it should be noted in the standard.


 int main(char[][] args)
 {
   int[char[]] intmap;
   
   int a = intmap["betty"];
   
   printf("a = %d\n",a);
 
   return 0;
 }
 

Pavel Minayev <evilone omen.ru> writes:

On Thu, 1 Aug 2002 02:12:31 +0000 (UTC) Patrick Down <pat codemoon.com> wrote:

 
 I'm a little surprised that this does not throw
 an error.  It prints a = 0.  When an assocative array
 doesn't have a key does it return the type.init
 value?


In fact, it _does_ create a key and initializes it with 
default value. This is a typical behaviour for associative
array in most languages, including std::map.