about pointer syntax

[bearophile]

spir:

> As a way to start learning D by practicing, I'm trying to implement a symbol table as linked list: see prototype code of the structs below. (Hints about good D coding welcome :-)

I have modified your code a little:

struct Symbol {
    string name;
    int element;
    Symbol* next;

    this(string n, int e, Symbol* s=null) {
        name = n;
        element = e;
        next = s;
    }
}

struct List {
    Symbol* first;

    int element(string name) {
        for (auto symbol = this.first; symbol != null; symbol = symbol.next)
            if (symbol.name == name)
                return symbol.element;
        return 0;
    }
}

void main() {
    auto l = List(new Symbol("baz", 3, new Symbol("bar", 2, new Symbol("foo", 1))));
    assert(l.element("bar") == 2);
}

- There's no need to initialize int to 0, string to "", pointers to null, etc, the compiler does it for you on default. Each type has a default init value (for floating point values it uses a NaN).
- Generally don't put a space before the ending semicolon.
- Four spaces indent and no space before the "*" of the pointer, as you have done, is OK.
- Using a while loop as you have done is OK, I have used a for loop just to show a shorter alternative.
- It's generally better to put one or two blank lines before structs, functions, etc
- (*symbol).name is written symbol.name in D.
- After an { generally a \n is used, there's no need to use the ; after the }
- using 0 as error return value is sometimes OK, but also keep in mind that exceptions are present.
- while(symbol) is acceptable, but some people prefer to put an explicit comparison to make the code more readable.
- sometimes using "auto" helps.
- In D linked lists are doable, but much less used, think about using a dynamic array, or even in this case an associative array:

void main() {
    auto aa = ["foo": 1, "bar": 2, "baz": 3];
    assert(aa["bar"] == 2);
}


> 1. To please the compiler, I had to wrap dereferencing in parens, like in "(*symbol).name". Is this just normal (for disambiguation)?
> 2. Just noticed the compiler accepts "symbol.name", while symbol is a pointer: is there implicit dereferencing of pointers to structs? If yes, does this also apply to pointers to arrays (for information, this what Oberon does).

Generally the field dereferencing doesn't require the "(*symbol).name", in D you use "symbol.name".
Pointers to arrays are possible, but quite uncommon in D.


> And a note: had forgotten to add an empty main(), just for compiling: the linker produced a rather big amount of error text without any hint to the actual issue. Maybe dmd could cope with that before calling gcc?

I agree, I have bug report 4680 open on something similar:
http://d.puremagic.com/issues/show_bug.cgi?id=4680


> Finally: the reference is rather harsh for me, esp there are very few example (I have few practice of C, and none of C++); the bits of tutorials I found are too light or just started (toc points to empty pages). Is there anywhere online a kind of D programming guide, even not polished or possibly unfinished (I know about the book; maybe I'll order it, but in meantime...).

The D2 documentation isn't abundant yet :-)

Bye,
bearophile