Add exercise: trinary

config.json

@@ -53,7 +53,7 @@
       "difficulty": 1,
       "topics": [
         "control-flow (conditionals)",
-				"integers", 
+				"integers",
 				"mathematics"
       ]
     },
@@ -76,6 +76,16 @@
         "unicode",
         "control-flow (if-else statements)"
       ]
+    },
+    {
+      "slug": "trinary",
+      "difficulty": 2,
+      "topics": [
+        "arrays",
+        "strings",
+        "integers",
+        "mathematics"
+      ]
     }
   ],
   "deprecated": [

exercises/trinary/example.jl

@@ -0,0 +1,4 @@
+function trinary_to_decimal(str::AbstractString)
+  typeof(match(r"^[0-2]+$", str)) == Void && return 0
+  mapreduce(i->(i[2]-'0')*3^i[1], +, zip(0:length(str), reverse(str)))
+end

exercises/trinary/runtests.jl

@@ -0,0 +1,47 @@
+using Base.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

exercises/trinary/trinary.jl

@@ -0,0 +1,3 @@
+function trinary_to_decimal(str::AbstractString)
+
+end