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to Trinary in the JavaScript Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Convert a trinary number, represented as a string (e.g. '102012'), to its decimal equivalent using first principles.

The program should consider strings specifying an invalid trinary as the value 0.

Trinary numbers contain three symbols: 0, 1, and 2.

The last place in a trinary number is the 1's place. The second to last is the 3's place, the third to last is the 9's place, etc.

# "102012"
    1       0       2       0       1       2    # the number
1*3^5 + 0*3^4 + 2*3^3 + 0*3^2 + 1*3^1 + 2*3^0    # the value
  243 +     0 +    54 +     0 +     3 +     2 =  302

If your language provides a method in the standard library to perform the conversion, pretend it doesn't exist and implement it yourself.

Setup

Go through the setup instructions for JavaScript to install the necessary dependencies:

http://exercism.io/languages/javascript/installation

Running the test suite

The provided test suite uses Jasmine. You can install it by opening a terminal window and running the following command:

npm install -g jasmine

Run the test suite from the exercise directory with:

jasmine trinary.spec.js

In many test suites all but the first test have been marked "pending". Once you get a test passing, activate the next one by changing xit to it.

Source

All of Computer Science http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

trinary.spec.js

var Trinary = require('./trinary');

describe('Trinary', function () {
  it('1 is decimal 1', function () {
    expect(new Trinary('1').toDecimal()).toEqual(1);
  });

  xit('2 is decimal 2', function () {
    expect(new Trinary('2').toDecimal()).toEqual(2);
  });

  xit('10 is decimal 3', function () {
    expect(new Trinary('10').toDecimal()).toEqual(3);
  });

  xit('11 is decimal 4', function () {
    expect(new Trinary('11').toDecimal()).toEqual(4);
  });

  xit('100 is decimal 9', function () {
    expect(new Trinary('100').toDecimal()).toEqual(9);
  });

  xit('112 is decimal 14', function () {
    expect(new Trinary('112').toDecimal()).toEqual(14);
  });

  xit('222 is 26', function () {
    expect(new Trinary('222').toDecimal()).toEqual(26);
  });

  xit('1122000120 is 32091', function () {
    expect(new Trinary('1122000120').toDecimal()).toEqual(32091);
  });

  xit('invalid trinary is decimal 0', function () {
    expect(new Trinary('carrot').toDecimal()).toEqual(0);
  });
});
function Trinary(string) {
  this.toDecimal = function() {
    if (isNaN(string)) return 0;
    var decimal=0;
    for (var x=0; x<string.length; ++x) {
      decimal += Math.pow(3,x) * string.charAt(string.length-x-1);
    }
    return decimal;
  }
}

module.exports=Trinary;

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