empty string & array truth values& comparisons to null

[spir]

Hello,


After the thread on "String to boolean inconsistency", here is a little comparison. I think it speaks by itself.

unittest {
    auto form = "%s %s   %s %s   %s %s";
    
    int[] a0;
    int[] a1 = [];
    writefln(form,
            a0?true:false, a1?true:false,
            a0 == null, a1 == null,
            a0 is null, a1 is null,
    );
    
    string s0;
    string s1 = "";
    writefln(form,
            s0?true:false, s1?true:false,
            s0 == null, s1 == null,
            s0 is null, s1 is null,
    );
    
    s1 = "".idup;
    writefln(form,
            s0?true:false, s1?true:false,
            s0 == null, s1 == null,
            s0 is null, s1 is null,
    );
    
    char[] s2 = "".dup;
    writefln(form,
            s0?true:false, s2?true:false,
            s0 == null, s2 == null,
            s0 is null, s2 is null,
    );
}

==>

false false   true true   true true
false true   true true   true false
false false   true true   true true
false false   true true   true true


Generally, should empty collections be considered false? What about uninitialised ones? Should .init of a collection be an empty one (or at least behave identically)?


Denis
-- -- -- -- -- -- --
vit esse estrany ☣

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