input/output parameters

From	Anton Shepelev <anton.txt@gmail.com>
Newsgroups	comp.lang.javascript
Subject	input/output parameters
Date	2021-03-13 15:32 +0300
Organization	A noiseless patient Spider
Message-ID	<20210313153232.40fa0c8b0adf07d7e807084d@gmail.com> (permalink)

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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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input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-13 15:32 +0300
  Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-13 15:16 +0000
    Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-14 18:51 +0300
      Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-14 16:15 +0000
        Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-14 18:31 +0000
          Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-14 22:27 +0300
            Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-14 23:44 +0000
            Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-15 06:41 -0700
        Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-14 22:17 +0300
          Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-14 23:28 +0000
          Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-15 06:39 -0700
      Re: input/output parameters Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-03-14 22:32 +0000
      Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-15 06:36 -0700
        Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-20 14:49 +0300
          Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-20 11:59 -0700
            Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-20 13:07 -0700
          Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-20 19:29 +0000
            Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-20 20:35 +0000
  Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-15 00:27 +0300
    Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-14 23:51 +0000
      Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-20 14:56 +0300
        Re: input/output parameters Jon Ribbens <jon+usenet@unequivocal.eu> - 2021-03-20 15:08 +0000
          Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-21 15:16 +0300
            Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-21 08:46 -0700
              Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-04-10 14:54 +0300
        Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-20 12:05 -0700
          Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-21 15:58 +0300
    Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-15 06:43 -0700
    Re: input/output parameters Silvio <silvio@internet.com> - 2021-03-15 18:01 +0100
      Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-16 18:06 +0000
        Re: input/output parameters Silvio <silvio@internet.com> - 2021-03-16 23:58 +0100
          Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-17 19:14 +0000
            Re: input/output parameters Silvio <silvio@internet.com> - 2021-03-17 23:46 +0100
              Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-18 18:04 +0000
                Re: input/output parameters Silvio <silvio@internet.com> - 2021-03-22 00:39 +0100
                Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-23 10:44 +0000
                Re: input/output parameters Silvio <silvio@internet.com> - 2021-03-30 00:33 +0200
                Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-31 19:53 +0100
                Re: input/output parameters Silvio <silvio@internet.com> - 2021-04-01 01:17 +0200
                Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-04-01 18:02 +0100
      Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-20 15:50 +0300
        Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-20 18:52 +0000
          Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-21 17:35 +0300
            Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-21 08:50 -0700
              Re: input/output parameters Anton Shepelev <anton.txt@gmail.com> - 2021-03-21 19:31 +0300
            Re: input/output parameters John G Harris <niam@jghnorth.org.uk.invalid> - 2021-03-21 19:27 +0000
        Re: input/output parameters "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-03-20 13:02 -0700
  Re: input/output parameters Postiljon Petskin <yyyyyyyyyyyywwwww@zohomail.eu> - 2023-04-22 08:47 -0700

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