# Trinary

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.

```bash
# "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.

## Getting Started

Make sure you have read [the C++ page](http://exercism.io/languages/cpp) on
exercism.io.  This covers the basic information on setting up the development
environment expected by the exercises.

## Passing the Tests

Get the first test compiling, linking and passing by following the [three
rules of test-driven development](http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd).
Create just enough structure by declaring namespaces, functions, classes,
etc., to satisfy any compiler errors and get the test to fail.  Then write
just enough code to get the test to pass.  Once you've done that,
uncomment the next test by moving the following line past the next test.

```C++
#if defined(EXERCISM_RUN_ALL_TESTS)
```

This may result in compile errors as new constructs may be invoked that
you haven't yet declared or defined.  Again, fix the compile errors minimally
to get a failing test, then change the code minimally to pass the test,
refactor your implementation for readability and expressiveness and then
go on to the next test.

Try to use standard C++11 facilities in preference to writing your own
low-level algorithms or facilities by hand.  [CppReference](http://en.cppreference.com/)
is a wiki reference to the C++ language and standard library.  If you
are new to C++, but have programmed in C, beware of
[C traps and pitfalls](http://www.slideshare.net/LegalizeAdulthood/c-traps-and-pitfalls-for-c-programmers).

## Source

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