On 5/11/2009 2:35 PM, grauzone wrote:
Tyro[a.c.edwards] wrote:
I am looking for a D version of scanf() but I'm sure there is no such
thing so I tried contrived one. I am sure I missed a slew of obvious
There's readf() in std.stream. I think you have to use std.cstream : din
to use it with stdin.
Thanks, but I'm trying to learn here... Hoping I can get a better
understanding of how things work or are supposed to work. I'll probably
change it back from read() to get().
int read(/+File inFile = stdin,+/ A...)(out A a) /+Uncommenting results
in: Error: arithmetic/string type expected for value-parameter, not
File+/
That would make inFile a template parameter, which obviously doesn't
make sense with objects, and I guess File is an object. This should work:
int read(A...)(File inFile, out A a)
OK... that works, but how would I set stdin as the default input "file"?
I tried: int read(A...)(out A a, File inFile = stdin) but the compiler
hangs trying to compile it whenever I call read() using 50% of the CPU
resource in the process.
{ start:
auto data = stripr(readln());
auto input = split(data);
string assign()
{
return
` try {
if(a.length != input.length)
return -1;
a[i] = to!(typeof(t))(input[i]);
} catch (ConvError e) {
writeln("Invalid input!");
goto start;
}`;
}
If the user types in too much or too less input, read() returns with an
error (-1), and the caller has to deal with it.
If the user typed in something unparseable, the function prompts an
error and lets the user retry.
This is inconsistent.
Got it... would it be better for the caller handles such problems or the
compiler?
Also, instead of using CTFE to return a const string, why not simply
const assign = ` .... ` ;
tried that but kept tying "string assign = " and "auto assign = "; both
of which kept failing until I placed it in a function. Thanks I have
changed it to enum.
You're using D 2.0, you probably have to replace "const" by "enum". I
don't know.
You use goto to retry. I'd replace it by a loop. If someone wants to
argue with me if goto is or is not evil, go ahead.
foreach(i, t; a)
{
static if(is(typeof(t) == void))
{}
else static if(is(typeof(t) == bool))
{}
bools can't be read? If the implementation is incomplete, there should
be at least an "assert(false);", maybe even a "static assert(false);".
Got it. What value would you read for a bool though? to me it can be
0||1, true||false, yes||no, etc... Would I simply use 0 && 1 and forget
about the rest?
else static if(is(typeof(t) == byte))
mixin(assign);
else static if(is(typeof(t) == ubyte))
mixin(assign);
else static if(is(typeof(t) == short))
mixin(assign);
else static if(is(typeof(t) == ushort))
mixin(assign);
else static if(is(typeof(t) == int))
mixin(assign);
else static if(is(typeof(t) == uint))
mixin(assign);
else static if(is(typeof(t) == long))
mixin(assign);
else static if(is(typeof(t) == ulong))
mixin(assign);
/+static if(is(typeof(t) == cent))
mixin(assign);
static if(is(typeof(t) == ucent))
mixin(assign);+/
else static if(is(typeof(t) == float))
mixin(assign);
else static if(is(typeof(t) == double))
mixin(assign);
else static if(is(typeof(t) == real))
mixin(assign);
Oh god, what the fuck! String mixins are the new #define! OK, at least
ROTFDWL - that was truly unexpected. Thanks.
this reduces the code duplication, but the code duplication shouldn't be
there in the first place.
You could just throw all the types into a tuple, and then foreach() on
it, checking for the type in each iteration.
Awesome... I didn't even think about that. Got it!
Or just make a single giant if() statement to check for all types to!()
supports (like if(is(typeof(t) == int) && is(typeof(t) == uint)...). In
any case, you could reduce the number of is() parts by using isNumeric()
from std.traits.
Or find a way to check for to!() supported data types automatically (but
I don't know to!() well enough if this is possible).
else static if(is(typeof(t) == ifloat))
a[i] = ifloat.max;
else static if(is(typeof(t) == idouble))
a[i] = idouble.max;
else static if(is(typeof(t) == ireal))
a[i] = ireal.max;
else static if(is(typeof(t) == cfloat))
a[i] = cfloat.max;
else static if(is(typeof(t) == cdouble))
a[i] = cdouble.max;
else static if(is(typeof(t) == creal))
a[i] = creal.max;
What?
That's a residue of my first try... I will take care of those. I really
should have replaced those with "assert(false);" because I didn't
understand how to implement them. Will read some more and try again in.
else static if(is(typeof(t) == char))
a[i] = input[i][0];
input could be an empty string, and random things could happen.
got it...
else static if(is(typeof(t) == wchar))
mixin(assign);
else static if(is(typeof(t) == dchar))
a[i] = input[i][0];
else static if(is(typeof(t) == string))
if(a.length > 1)
a[i] = input[i];
else
a[i] = data;
I see, if the caller of the function only requests a char[], the
splitting by white space is disregarded, and the whole string is
returned. Isn't that a but inconsistent? At least, it could always
return the remainder of the string, if this char[] parameter is the last
of the function.
I was actually hoping to find a way to put the unused portion back unto
the buffer but that seems a much better approach.
Also, the array index i isn't checked for input, and random things could
happen. (You'd get an exception in debug mode, but not in release mode.)
??? not sure what you mean here. i is the index of the variable as it
appears in the tuple "A". Why would I need to check it for input? i is
valid as long as we have not reached the end of the tuple.
Also, http://en.wikipedia.org/wiki/Dangling_else
Some more reading to do... got it!
else static if(is(typeof(t) == dstring))
{}
else static if(is(typeof(t) == char[]))
a[i] = stripr(data).dup;
Shouldn't split() already remove all white space?
split removes the white space but only from the copy of the string
returned. The original remains untouched.
}
return 0;
}
Thank you very much for responding.
Andrew
