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digitalmars.D.learn - Catching array out of bounds

reply jicman <cabrera_ _wrc.xerox.com> writes:
Greetings!

I have this program,

import std.stdio;
void main()
{
  char[][] a = ["a","b","c"];
  try
  {
    writefln(a[3]);
  }
  catch (ArrayBoundsError)
  {
    writefln("error...");
  }
}

when I compile it, I get,

23:53:52.73>build -I..;c:\D\dmd\import array.d
array.d(10): Error: identifier 'ArrayBoundsError' is not defined
array.d(10): Error: ArrayBoundsError is used as a type
Error: can only catch class objects, not 'void'

This is right from the D1 Arrays help...

http://www.digitalmars.com/d/1.0/arrays.html

What am I doing wrong?

thanks,

josé
Nov 04 2009
parent reply Justin Johansson <no spam.com> writes:
jicman Wrote:


 Greetings!
 
 I have this program,
 
 import std.stdio;
 void main()
 {
   char[][] a = ["a","b","c"];
   try
   {
     writefln(a[3]);
   }
   catch (ArrayBoundsError)
   {
     writefln("error...");
   }
 }
 
 when I compile it, I get,
 
 23:53:52.73>build -I..;c:\D\dmd\import array.d
 array.d(10): Error: identifier 'ArrayBoundsError' is not defined
 array.d(10): Error: ArrayBoundsError is used as a type
 Error: can only catch class objects, not 'void'
 
 This is right from the D1 Arrays help...
 
 http://www.digitalmars.com/d/1.0/arrays.html
 
 What am I doing wrong?
 
 thanks,
 
 josé
 


Hi josé,

You don't import modules as you show:
build -I..;c:\D\dmd\import array.d

You should be importing the array module into
your program using the following statement.

import std.array;

Also (and I' not 100% sure about this) that you might need to
declare a variable along with the catch statement like as follows
(at least that's what I always do regardless of whether or
not it may be omitted) ...

catch (ArrayBoundsError e) {
...
}

Good luck with your further D adventures,

Justin Johansson
Nov 04 2009
next sibling parent reply grauzone <none example.net> writes:
Justin Johansson wrote:

 Also (and I' not 100% sure about this) that you might need to
 declare a variable along with the catch statement like as follows
 (at least that's what I always do regardless of whether or
 not it may be omitted) ...


And he should remember that out of bounds checking is enabled only in 
debug builds. In release builds, out of bounds accesses will simply lead 
to undefined behavior.
Nov 05 2009
parent reply jicman <cabrera_ _wrc.xerox.com> writes:
grauzone Wrote:


 Justin Johansson wrote:

 Also (and I' not 100% sure about this) that you might need to
 declare a variable along with the catch statement like as follows
 (at least that's what I always do regardless of whether or
 not it may be omitted) ...


 
 And he should remember that out of bounds checking is enabled only in 
 debug builds. In release builds, out of bounds accesses will simply lead 
 to undefined behavior.


Ok, I will bite...  And why, then, it is in the array help as an option to
catch the out of bounds?
Nov 05 2009
parent grauzone <none example.net> writes:
jicman wrote:

 grauzone Wrote:
 

 Justin Johansson wrote:

 Also (and I' not 100% sure about this) that you might need to
 declare a variable along with the catch statement like as follows
 (at least that's what I always do regardless of whether or
 not it may be omitted) ...


 And he should remember that out of bounds checking is enabled only in 
 debug builds. In release builds, out of bounds accesses will simply lead 
 to undefined behavior.


 
 Ok, I will bite...  And why, then, it is in the array help as an option to
catch the out of bounds?


I don't quite get what you're saying, but here's the bit of the 
documentation that says that out of bounds checking is an optional 
debugging feature:

"A program may not rely on array bounds checking happening"
http://www.digitalmars.com/d/1.0/arrays.html

You can try it yourself. Just compile the program with -release. No out 
of bounds error will be thrown; instead the program may behave 
abnormally or crash (or the error remains silent).
Nov 05 2009
prev sibling parent reply jicman <cabrera_ _wrc.xerox.com> writes:
Justin Johansson Wrote:


 jicman Wrote:
 

 Greetings!
 
 I have this program,
 
 import std.stdio;
 void main()
 {
   char[][] a = ["a","b","c"];
   try
   {
     writefln(a[3]);
   }
   catch (ArrayBoundsError)
   {
     writefln("error...");
   }
 }
 
 when I compile it, I get,
 
 23:53:52.73>build -I..;c:\D\dmd\import array.d
 array.d(10): Error: identifier 'ArrayBoundsError' is not defined
 array.d(10): Error: ArrayBoundsError is used as a type
 Error: can only catch class objects, not 'void'
 
 This is right from the D1 Arrays help...
 
 http://www.digitalmars.com/d/1.0/arrays.html
 
 What am I doing wrong?
 
 thanks,
 
 josé
 


 
 Hi josé,


Hi Justin.


 
 You don't import modules as you show:
 build -I..;c:\D\dmd\import array.d


I am giving the path of where the modules are.  The array.d is the program that
contains the above code.


 
 You should be importing the array module into
 your program using the following statement.
 
 import std.array;


there is no module std.array for D1.  I don't know about D2, but D1 does not
have it.


 Also (and I' not 100% sure about this) that you might need to
 declare a variable along with the catch statement like as follows
 (at least that's what I always do regardless of whether or
 not it may be omitted) ...
 
 catch (ArrayBoundsError e) {
 ...
 }


I tried that also.  :-) Did you even try the little program?  Copy and paste to
your favorite editor and give it a try. :-)

 


Anybody else can provide me what is wrong with the program above?

thanks,

josé
Nov 05 2009
parent reply "Lars T. Kyllingstad" <public kyllingen.NOSPAMnet> writes:
jicman wrote:

 Justin Johansson Wrote:
 

 jicman Wrote:


 Greetings!

 I have this program,

 import std.stdio;
 void main()
 {
   char[][] a = ["a","b","c"];
   try
   {
     writefln(a[3]);
   }
   catch (ArrayBoundsError)
   {
     writefln("error...");
   }
 }

 when I compile it, I get,

 23:53:52.73>build -I..;c:\D\dmd\import array.d
 array.d(10): Error: identifier 'ArrayBoundsError' is not defined
 array.d(10): Error: ArrayBoundsError is used as a type
 Error: can only catch class objects, not 'void'

 This is right from the D1 Arrays help...

 http://www.digitalmars.com/d/1.0/arrays.html

 What am I doing wrong?

 thanks,

 josé


 Hi josé,


 Hi Justin.
 

 You don't import modules as you show:
 build -I..;c:\D\dmd\import array.d


 I am giving the path of where the modules are.  The array.d is the program
that contains the above code.
 

 You should be importing the array module into
 your program using the following statement.

 import std.array;


 there is no module std.array for D1.  I don't know about D2, but D1 does not
have it.
 

 Also (and I' not 100% sure about this) that you might need to
 declare a variable along with the catch statement like as follows
 (at least that's what I always do regardless of whether or
 not it may be omitted) ...

 catch (ArrayBoundsError e) {
 ...
 }


 I tried that also.  :-) Did you even try the little program?  Copy and paste
to your favorite editor and give it a try. :-)
 
 Anybody else can provide me what is wrong with the program above?
 
 thanks,
 
 josé



Actually, there is a module called std.array in D1 as well. For some 
reason it's just not in the documentation on the homepage. The 
ArrayBoundsError class is defined in there. Try importing it, and see if 
that works. (I can't test it, as I'm using D2 myself.)

Alternatively, write catch(Exception e) or catch(Error e). Both of them 
are defined in object.d and are always available.

-Lars

-Lars
Nov 05 2009
parent "Lars T. Kyllingstad" <public kyllingen.NOSPAMnet> writes:
Lars T. Kyllingstad wrote:

 jicman wrote:

 Justin Johansson Wrote:


 jicman Wrote:


 Greetings!

 I have this program,

 import std.stdio;
 void main()
 {
   char[][] a = ["a","b","c"];
   try
   {
     writefln(a[3]);
   }
   catch (ArrayBoundsError)
   {
     writefln("error...");
   }
 }

 when I compile it, I get,

 23:53:52.73>build -I..;c:\D\dmd\import array.d
 array.d(10): Error: identifier 'ArrayBoundsError' is not defined
 array.d(10): Error: ArrayBoundsError is used as a type
 Error: can only catch class objects, not 'void'

 This is right from the D1 Arrays help...

 http://www.digitalmars.com/d/1.0/arrays.html

 What am I doing wrong?

 thanks,

 josé


 Hi josé,


 Hi Justin.


 You don't import modules as you show:
 build -I..;c:\D\dmd\import array.d


 I am giving the path of where the modules are.  The array.d is the 
 program that contains the above code.


 You should be importing the array module into
 your program using the following statement.

 import std.array;


 there is no module std.array for D1.  I don't know about D2, but D1 
 does not have it.


 Also (and I' not 100% sure about this) that you might need to
 declare a variable along with the catch statement like as follows
 (at least that's what I always do regardless of whether or
 not it may be omitted) ...

 catch (ArrayBoundsError e) {
 ...
 }


 I tried that also.  :-) Did you even try the little program?  Copy and 
 paste to your favorite editor and give it a try. :-)

 Anybody else can provide me what is wrong with the program above?

 thanks,

 josé


 
 
 Actually, there is a module called std.array in D1 as well. For some 
 reason it's just not in the documentation on the homepage. The 
 ArrayBoundsError class is defined in there. Try importing it, and see if 
 that works. (I can't test it, as I'm using D2 myself.)
 
 Alternatively, write catch(Exception e) or catch(Error e). Both of them 
 are defined in object.d and are always available.


...or don't. Like grauzone pointed out, you shouldn't rely on array 
bounds being checked. That's probably why std.array isn't in the docs.

-Lars
Nov 05 2009