I think I got a handle on D's static and dynamic arrays, till I come to std.array and see all the shiny new tools. I can understand all the replace.. functions, but the appender function gave me pause. The documentation says appender "Returns a new Appender or RefAppender initialized with a given array."

My first thought that doesn't D's built in arrays already allow appending? (at least for dynamic arrays) And the example shows the use of appender with string. Isn't string an immutable array or characters? Wouldn't this be the last data type you would want to be appending to? Another thing that had me wondering is the use of put() down below; doesn't the append syntax (~=) give you the same exact functionality; so why bother?

void main()
    import std.array;
    import std.stdio: write, writeln, writef, writefln;
    auto w = appender!string;
    // pre-allocate space (this avoids costly reallocations)
    assert(w.capacity >= 10);

    w.put('a'); // single elements
    w.put("bc"); // multiple elements

    // use the append syntax
    w ~= 'd';
    w ~= "ef";

    writeln(w.data); // "abcdef"

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