[Issue 17628] formattedWrite is impure on double

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17628

--- Comment #1 from Vladimir Panteleev <dlang-bugzilla at thecybershadow.net> ---
Missing:
    import std.array : appender;

Seems to be impure because it calls snprintf (which I think may change FPU
flags or something).

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