• nojoking <kuangdong gmail.com> Sep 24 2006
• Chris Nicholson-Sauls <ibisbasenji gmail.com> Sep 24 2006

nojoking <kuangdong gmail.com> writes:

How to return different types?For Example:

test.d
/++/
import std.stdio;

void main()
{
Test test;
test["a"]="A string. ";
test["b"]=1234;
test["c"]=true;

writefln(test["a"],test["b"],test["c"]);
}

struct Test
{
char[][char[]] strarr;
int[char[]] intarr;
bool[char[]] bolarr;

void opIndexAssign(int value,char[] key)
{
intarr[key]=value;
}
void opIndexAssign(char[] value,char[] key)
{
strarr[key]=value;
}
void opIndexAssign(bool value,char[] key)
{
bolarr[key]=value;
}
/+???????????????????
opIndex(char[] key)
{
}
???????????????????+/
}

Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:

nojoking wrote:
 How to return different types?For Example:
 
 test.d
 /++/
 import std.stdio;
 
 void main()
 {
 Test test;
 test["a"]="A string. ";
 test["b"]=1234;
 test["c"]=true;
 
 writefln(test["a"],test["b"],test["c"]);
 }
 
 struct Test
 {
 char[][char[]] strarr;
 int[char[]] intarr;
 bool[char[]] bolarr;
 
 void opIndexAssign(int value,char[] key)
 {
 intarr[key]=value;
 }
 void opIndexAssign(char[] value,char[] key)
 {
 strarr[key]=value;
 }
 void opIndexAssign(bool value,char[] key)
 {
 bolarr[key]=value;
 }
 /+???????????????????
 opIndex(char[] key)
 {
 }
 ???????????????????+/
 }


Strictly speaking, you can't.  There is no overloading on return type.  What
you can do, 
however, is to return a Box (see: std.boxer) or write and return a Var struct,
such as this:

# struct Var {
#   static enum Type { Str, Int, Bool }
#
#   Type type ;
#   union {
#     char[] s ;
#     int    i ;
#     bool   b ;
#   }
# }

In which case your opIndex could be something like:

# Var opIndex (char[] key) {
#   Var result ;
#
#   if (auto x = key in strarr) {
#     result.type = Type.Str ;
#     result.s    = (*x).dup ;
#   }
#   else if (auto y = key in intarr) {
#     result.type = Type.Int ;
#     result.i    = *y       ;
#   }
#   else if (auto z = key in bolarr) {
#     result.type = Type.Bool ;
#     result.b    = *z        ;
#   }
#   else {
#     throw new Exception("key not found: '" ~ key ~ "'");
#   }
# }

-- Chris Nicholson-Sauls