can't compile a simple class

[Patrick Tinkham]

Sorry for the question. I am a n00b to D. I tried to compile the 
following code from Alexandrescu's book:

import std.stdio;
class A {
   int x = 42;
}

unittest {
   auto a1 = new A;
   assert (a1.x == 42);
   auto a2 = a1;
   a2.x = 100;
   assert (a1.x == 100);
}

at the command line:

/d$ dmd c.d
/usr/lib/i386-linux-gnu/libphobos2.a(dmain2_473_1a5.o): In 
function `main':
src/rt/dmain2.d:(.text.main+0x4): undefined reference to `_Dmain'
/usr/lib/i386-linux-gnu/libphobos2.a(deh2_453_525.o): In function 
`_D2rt4deh213__eh_finddataFPvZPS2rt4deh29FuncTable':
src/rt/deh2.d:(.text._D2rt4deh213__eh_finddataFPvZPS2rt4deh29FuncTable+0x4): 
undefined reference to `_deh_beg'
src/rt/deh2.d:(.text._D2rt4deh213__eh_finddataFPvZPS2rt4deh29FuncTable+0xc): 
undefined reference to `_deh_beg'
src/rt/deh2.d:(.text._D2rt4deh213__eh_finddataFPvZPS2rt4deh29FuncTable+0x12): 
undefined reference to `_deh_end'

...

plus much more encrypted Klingon.

Help?