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digitalmars.D.learn - integer cast in object_.d

reply Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
I'm looking at compare() in class TypeInfo_Array and it's defined as:

override int compare(in void* p1, in void* p2)
{
    void[] a1 = *cast(void[]*)p1;
    void[] a2 = *cast(void[]*)p2;
    size_t sz = value.tsize();
    size_t len = a1.length;

    if (a2.length < len)
        len = a2.length;
    for (size_t u = 0; u < len; u++)
    {
        int result = value.compare(a1.ptr + u * sz, a2.ptr + u * sz);
        if (result)
            return result;
    }
    return cast(int)a1.length - cast(int)a2.length;
}

Shouldn't that return line be:
return cast(int)(a1.length - a2.length);

To make it 64-bit safe?
Sep 04 2011
next sibling parent Timon Gehr <timon.gehr gmx.ch> writes:
On 09/05/2011 04:57 AM, Andrej Mitrovic wrote:
 I'm looking at compare() in class TypeInfo_Array and it's defined as:

 override int compare(in void* p1, in void* p2)
 {
      void[] a1 = *cast(void[]*)p1;
      void[] a2 = *cast(void[]*)p2;
      size_t sz = value.tsize();
      size_t len = a1.length;

      if (a2.length<  len)
          len = a2.length;
      for (size_t u = 0; u<  len; u++)
      {
          int result = value.compare(a1.ptr + u * sz, a2.ptr + u * sz);
          if (result)
              return result;
      }
      return cast(int)a1.length - cast(int)a2.length;
 }

 Shouldn't that return line be:
 return cast(int)(a1.length - a2.length);

 To make it 64-bit safe?

Both are not 64-bit safe.
Sep 04 2011
prev sibling parent Michel Fortin <michel.fortin michelf.com> writes:
On 2011-09-05 02:57:33 +0000, Andrej Mitrovic 
<andrej.mitrovich gmail.com> said:

 I'm looking at compare() in class TypeInfo_Array and it's defined as:
 
 override int compare(in void* p1, in void* p2)
 {
     void[] a1 = *cast(void[]*)p1;
     void[] a2 = *cast(void[]*)p2;
     size_t sz = value.tsize();
     size_t len = a1.length;
 
     if (a2.length < len)
         len = a2.length;
     for (size_t u = 0; u < len; u++)
     {
         int result = value.compare(a1.ptr + u * sz, a2.ptr + u * sz);
         if (result)
             return result;
     }
     return cast(int)a1.length - cast(int)a2.length;
 }
 
 Shouldn't that return line be:
 return cast(int)(a1.length - a2.length);
 
 To make it 64-bit safe?

Per the rules of modular arithmetic substraction, both will give you the same result actually. And no it isn't 64-bit safe. -- Michel Fortin michel.fortin michelf.com http://michelf.com/
Sep 04 2011