On Saturday, March 13, 2021 at 2:32:40 PM UTC+2, Anton Shepelev wrote:
> Hello, all
>
> I started learning JavaScript but yesterday, but am already
> stuck at implementing input/output parameters. As I
> understand, they are not part of the language, yet I find
> them very convenient for normal procedural programming. For
> example, they allow returning a boolean flag and using
> functions inside `if` tests, similar to the very convenient
> TryParse() and TryGetValue() functions in C#:
>
> TryParse: https://docs.microsoft.com/en-us/dotnet/api/system.int32.tryparse
> TryGetValue: https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2.trygetvalue
>
> Unfortunately for me, JavaScript seems to compensate the
> lack of in/out parameters with much more complicated
> functional and object-oriented mechanisms. I therefore have
> tried to implement them myself, but have not come up with a
> satisfactory solution. The examples below demonstrate a
> function for integer division that stores the result in
> variable and returns a boolean value indicating whether the
> division was exact:
>
> // for bi-direction in/out parameters, return a code that
> // creates an anonymous object storing the the value *and*
> // setter clousure:
>
> function out_1(vn)
> { return "x => " + vn + " = x"; }
>
> function int_div_1(a, b ,c)
> { var /*integer */ r; // ratio
> var /*boolean */ x; // result is exact
>
> r = Math.floor(a / b);
> x = r * b === a;
> c( r );
> return x;
> }
>
> function out_2( vn, val, ret )
> { return `${vn} = ${val}, ${ret}`; }
>
> function int_div_2(a, b, vn)
> { var /*integer */ r; // ratio
> var /*boolean */ x; // result is exact
>
> r = Math.floor(a / b);
> x = r * b === a;
> return out_2(vn, r, x);
> }
>
> { let /*integer */ ratio;
> let /*boolean */ exact;
>
> exact = int_div_1(7, 3, eval(out_1("ratio")));
> console.log(`7/3: ratio = ${ratio}; exact = ${exact}.`);
>
> exact = int_div_1(6, 3, eval(out_1("r")));
> console.log(`6/3: ratio = ${ratio}; exact = ${exact}.`);
>
> exact = eval(int_div_2(7, 3, "ratio"));
> console.log(`7/3: ratio = ${ratio}; exact = ${exact}.`);
>
> exact = eval(int_div_2(6, 3, "ratio"));
> console.log(`6/3: ratio = ${ratio}; exact = ${exact}.`);
> }
>
> Can you think of better way to emulate output parameters,
> and preferable also bi-directional input/output parameters?
>
> --
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> /\ http://preview.tinyurl.com/qcy6mjc [archived]

You agree, that You are the most unoriginal person in the history of the universe ?