readf anyone?

[Tyro]

So I'm digging in and enjoying the read (and let me tell you it's a
pretty interesting read), then I flip to page 22 (I read slow) and
stumbled onto this code:

for (double x; readf(" % ", &x) == 1; ) {
   [snip]
}

Wait that don't look right. I don't remember readf() being
implemented. So I decided to check things out. I jimmied up this
little rig:

void main() {
	double q;
	readf("%s", &q);
	writeln(q);
}

and launched it:

D:\code>dmd input
input.d(5): Error: undefined identifier readf, did you mean function
readln?

well that didn't work. Maybe I'm missing something. Let me take a
look an the phobos doc: no, no mention there. Oh, I got it, I don't
have the latest compiler (how stupid of me). Downloading...
Installing... recompiling. Damn, that wasn't it. Ok, let me take a
look at std.stdio.d. There it is, it's a member function of class
File. Ok, I should be able to access it through stdin. Let me try
that instead:

void main() {
	double q;
	stdin.readf("%s", &q);
	writeln(q);
}

Here goes nothing:

D:\code>dmd read
d:\dmd2\windows\bin\..\..\src\phobos\std\format.d(2948): Error: no
property 'len
gth' for type 'InputByChar'

Damn, that didn't work either. Now that's crazy, why would we use
this function in the book and not take the extra effort to ensure
that it's actually implemented before going to print? Was this an
oversight? If so, can we please get the fix.