Titanion 0.4 + Phobos2 bug

[bearophile]

Robert Jacques:

> struct Vec(T = float,size_t N = 3) {
>      T[N] _data;
>      alias _data this;
>      string toString() { std.conv.return text(_data); }
> }

Very nice.


> plus functions as array properties which apparently got upgraded at some  
> point to the extra () isn't needed anymore. ( i.e. vec.x instead of  
> vec.x() )
> 
> i.e.
> 
> T x(T, size_t N)(T[N] v) {
>      return v[0];
> }

A name like "x" is too much common, I don't like that as free function.

I like this better (I have borrowed SeriesGen2 from my D1 dlibs):

import std.string: toString, writeln;
import std.conv: to;
import std.metastrings: Format, ToString;

template SeriesGen2(string txt, string separator, int max, int min=0) {
    static if (min > max)
        const SeriesGen2 = "";
    else static if (min == max)
        const SeriesGen2 = Format!(txt, ToString!(max),
                                        ToString!(max));
    else
        const SeriesGen2 = SeriesGen2!(txt, separator, max-1, min) ~ separator ~
                           Format!(txt, ToString!(max),
                                        ToString!(max));
}

struct Vec(T=float, size_t N=3) {
    static assert(N > 0);
    T[N] _data;
    alias _data this;
    string toString() { return to!string(this._data); }

    // You may also use SeriesGen4 here
    mixin(SeriesGen2!("T d%s(size_t i){ return this._data[%s]; }", "\n", N-1));
    mixin(SeriesGen2!("void d%s(T value){ this._data[%s] = value; }", "\n", N-1));
}

Vec!(T, N) foo(T, size_t N)(T[N] v) {
    Vec!(T,N) r = v;
    return r;
}

void main() {
    float[3] a = [1,2,3];
    auto v = foo(a);
    writeln(v, " ", a[2], " ", v.d1);
    v.d0 = 5;
    writeln(v);
}


Unfortunately I think I have found another bug. If I run:

import std.metastrings: Format;
pragma(msg, Format!("good %s test", 5));
void main() {}


D1 outputs correctly:
good 5 test

But D2 outputs the wrong:
good %s test5

This also may mean that std.metastrings module lacks compile-time unittests (some static asserts suffice).

Bye,
bearophile