CMJones001's solution to Trinary on the Julia track

Instructions

Test suite

Solution

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.

Source

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

Version compatibility

This exercise has been tested on Julia versions >=1.0.

Submitting Incomplete Solutions

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

runtests.jl

using Test

include("trinary.jl")

@testset "trinary 1 is decimal 1" begin
    @test trinary_to_decimal("1") == 1
end

@testset "trinary 2 is decimal 2" begin
    @test trinary_to_decimal("2") == 2
end

@testset "trinary 10 is decimal 3" begin
    @test trinary_to_decimal("10") == 3
end

@testset "trinary 11 is decimal 4" begin
    @test trinary_to_decimal("11") == 4
end

@testset "trinary 100 is decimal 9" begin
    @test trinary_to_decimal("100") == 9
end

@testset "trinary 112 is decimal 14" begin
    @test trinary_to_decimal("112") == 14
end

@testset "trinary 222 is decimal 26" begin
    @test trinary_to_decimal("222") == 26
end

@testset "trinary 1122000120 is decimal 32091" begin
    @test trinary_to_decimal("1122000120") == 32091
end

@testset "invalid trinary digits returns 0" begin
    @test trinary_to_decimal("1234") == 0
end

@testset "invalid word as input returns 0" begin
    @test trinary_to_decimal("carrot") == 0
end

@testset "invalid numbers with letters as input returns 0" begin
    @test trinary_to_decimal("0a1b2c") == 0
end

function trinary_to_decimal(str)
    is_valid(x) = 0x30 <= codepoint(x) <= 0x32
    all([is_valid(digit) for digit in str]) || return 0

    raise((index, digit)) = codepoint(digit - 0x30) * 3^(index-1)
    mapreduce(raise, +, enumerate(reverse(str)); init=0)
end

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CMJones001's solution

to Trinary in the Julia Track