Re: New to D: parse a binary file
scottrick Wrote:
T[] rawRead(T)(T[] buffer);
I understand that T is generic type, but I am not sure of the
meaning of the (T) after the method name.
That T is defining the symbol to represent the generic type. It can have more
than one and D provides other things like aliases... Another way to write that
function (I may get something wrong here but give it a shot) is:
template(T) {
T[] rawRead(T[] buffer);
}
Re: New to D: parse a binary file
Thanks, your post was very helpful. Two more questions (probably related): Where is the function 'format' defined? Also, what is that 'unittest' block? It compiles fine as is, but if I refer to format outside of unittest, it will not compile. Also, if I compile and run your example, it doesn't do anything, since main() is empty? Thanks again,
Re: New to D: parse a binary file
scottrick: Where is the function 'format' defined? You need to add at the top of the module: import std.conv: format; Or: import std.conv; Also, what is that 'unittest' block? It compiles fine as is, but if I refer to format outside of unittest, it will not compile. Also, if I compile and run your example, it doesn't do anything, since main() is empty? It's an block of unit tests :-) Currently in your program they are not even compiled, so the format is not used. To run the unit tests you need to compile with -unittest compiler switch (with DMD). See also: http://www.digitalmars.com/d/2.0/unittest.html Bye, bearophile
Re: New to D: parse a binary file
Am 06.02.2011 19:38, schrieb Jesse Phillips:
scottrick Wrote:
T[] rawRead(T)(T[] buffer);
I understand that T is generic type, but I am not sure of the
meaning of the (T) after the method name.
That T is defining the symbol to represent the generic type. It can have more
than one and D provides other things like aliases... Another way to write that
function (I may get something wrong here but give it a shot) is:
template(T) {
T[] rawRead(T[] buffer);
}
I think you meant
template(T) rawRead{
T[] rawRead(T[] buffer);
}
'template' defines a namespace which is normally accessed like
templ!(parameters).member;
templ!(parameters).memberfunc(parameters);
Because the template and it's member are called identically this member
is accessed autoatically (the eponymous-trick). If it's a function you
call it like that:
templfunc!(compiletimeparam)(param);
The compile time parameters can left out, if these can be derived from
the normal parameters' type.
templfun(param);
Voilla! You have a completely transparent templated func.
Mafi
Re: New to D: parse a binary file
On 02/05/2011 06:26 PM, scottrick wrote:
Hi,
I am new to D. I am trying to write a binary file parser for a
project of mine and I thought it would be fun to try and learn a new
language at the same time. So I chose D! :D I have been
struggling however and have not been able to find very many good
examples, so I am posting this message.
I think I'm supposed to be using std.stdio, but I'm not 100% sure.
Could somebody post a short example of how to parse a couple of
characters and ints or whatever from a file? Or how to read, say,
the next however many bytes into a struct?
Also, looking at the documentation, I am confused by this method
signature:
T[] rawRead(T)(T[] buffer);
I understand that T is generic type, but I am not sure of the
meaning of the (T) after the method name.
Thanks,
Below a pair of examples that should make all this clearer: a templated
hand-written naive map func, and a template struct type (would be nearly the
same for a class). Just run it. Additional explanations on demand.
import File=std.file;
import std.array;
Out[] map (In, Out) (In[] source, Out delegate (In) f) {
// (0)
Out[] target;
foreach (element; source)
target ~= f(element);
return target;
}
struct StoreStack (T) {
T[] items;
string logFileName;
this (string logFileName, T[] items=[]) {
this.items = items;
this.logFileName = logFileName;
// create/reset log file
File.write(logFileName, );
}
string toString () {
static form = StoreStack(\%s\, %s);
return format(form, this.logFileName, this.items);
}
void put (T item) {
this.items ~= item;
string message = format(put item: %s\n, item);
File.append(logFileName, message);
}
T take () {
T item = this.items[$-1];
this.items = this.items[0..$-1];
string message = format(took item: %s\n, item);
File.append(logFileName, message);
return item;
}
}
unittest {
// map
string hex (uint i) { return format(0x%03X, i); }
uint[] decs = [1, 3, 9, 27, 81, 243, 729];
auto hexes = map!(uint,string)(decs, hex);
// auto hexes = map(decs, hex); // (1)
writefln (decs: %s\n--\nhexes: %s, decs, hexes);
writeln();
// StoreStack
auto store = StoreStack!(int)(test_log);
// auto store = StoreStack!int(test_log); // (2)
store.put(3); store.put(2); store.put(3);
auto i = store.take();
writefln(store: %s, store);
writefln(log:\n%s, File.readText(test_log));
}
void main() {}
(0) The func must be declared as delegate (instead of simple func pointer)
because: the actual func hex beeing defined in a block, the compiler turns it
into a delegate. Detail.
(1) Here, the compiler is able to infer the template parameters (types): no
need to specify them.
(2) When there is a single template parameter, the syntax allows omitting ()
around it.
Denis
--
_
vita es estrany
spir.wikidot.com
Re: New to D: parse a binary file
spir:
Out[] map (In, Out) (In[] source, Out delegate (In) f) {
// (0)
...
string hex (uint i) { return format(0x%03X, i); }
uint[] decs = [1, 3, 9, 27, 81, 243, 729];
auto hexes = map!(uint,string)(decs, hex);
...
(0) The func must be declared as delegate (instead of simple func pointer)
because: the actual func hex beeing defined in a block, the compiler turns it
into a delegate. Detail.
See also:
void foo(In, Out)(Out function(In) f) {}
void main() {
static int bar(int i) { return 0; }
foo(bar);
}
Bye,
bearophile
