onDispatch demo not compiling

[Shachar via Digitalmars-d-learn]

I'm trying to compile the onDispatch demo program from "The D 
Programming Language" (page 387). At first I had an import 
problem, but I fixed that. Now, however, when I try to call 
"a.do_something_cool", I get an error message saying:


onDispatch.d(43): Error: no property 'do_something_cool' for type 
'onDispatch.A'


Full program follows (into onDispatch.d):
import core.stdc.ctype;
import std.stdio;

string underscoresToCamelCase(string sym) {
string result;
result.reserve(sym.length);
bool makeUpper;
foreach (c; sym) {
if (c == '_') {
makeUpper = true;
} else {
if (makeUpper) {
result ~= toupper(c);
makeUpper = false;
} else {
result ~= c;
}
}
}
return result;
}

unittest {
assert(underscoresToCamelCase("hello_world") == "helloWorld");
assert(underscoresToCamelCase("_a") == "A");
assert(underscoresToCamelCase("abc") == "abc");
assert(underscoresToCamelCase("a_bc_d_") == "aBcD");
}

class A {
auto onDispatch(string m, Args...)(Args args) {
// return 
mixin("this."~underscoresToCamelCase(m)~"(args)");

}

void doSomethingCool(int x, int y) {
writeln("Do something cool");
}
}

unittest {
auto a = new A;
a.doSomethingCool(5, 6);
a.do_something_cool(5, 6);
}

Re: onDispatch demo not compiling

[Shachar via Digitalmars-d-learn]

On Thursday, 21 August 2014 at 06:11:06 UTC, ketmar via 
Digitalmars-d-learn wrote:

that will do the trick.

Indeed. I ended up simply directly calling 
"a.opDispatch!"do_something_cool"(5, 6)", which brought most of 
those issues to light.


Shachar

Why is this pure?

[Shachar via Digitalmars-d-learn]

The following program compiles, and does what you'd expect:

struct A {
int a;
}

pure int func( ref A a )
{
return a.a += 3;
}

As far as I can tell, however, it shouldn't. I don't see how or 
why func can possibly be considered pure, as it changes a state 
external to the function.


What am I missing? Or is this just a compiler bug?

Shachar

Why does this not work?

[Shachar via Digitalmars-d-learn]

void func( int c )
{
ubyte a;

a = cast(ubyte)c + cast(ubyte)c;
}

dmd v2.065 complains about:
test.d(5): Error: cannot implicitly convert expression 
(cast(int)cast(ubyte)c + cast(int)cast(ubyte)c) of type int to 
ubyte


As far as I can tell, adding two values of the same type should 
result in the same type.


Shachar

Re: Why does this not work?

[Shachar via Digitalmars-d-learn]

On Wednesday, 17 September 2014 at 13:03:05 UTC, flamencofantasy 
wrote:

the result of ubyte + ubyte is int I believe.

Try;
void func( int c )
{
 ubyte a;

 a = cast(ubyte)(cast(ubyte)c + cast(ubyte)c);
}


From http://dlang.org/type, under Usual Arithmetic Conversions:
4. Else the integer promotions are done on each operand, followed 
by:

1. If both are the same type, no more conversions are done.

So, as far as I can see, the specs disagree with you.

Shachar