Sync protein-translation tests (#225)

* Sync `protein-translation` tests

* Fix typo in test name

exercises/practice/protein-translation/.meta/tests.toml

@@ -87,11 +87,15 @@ description = "Translation stops if STOP codon in middle of three-codon sequence
 [2c2a2a60-401f-4a80-b977-e0715b23b93d]
 description = "Translation stops if STOP codon in middle of six-codon sequence"
 
+[f6f92714-769f-4187-9524-e353e8a41a80]
+description = "Sequence of two non-STOP codons does not translate to a STOP codon"
+
 [1e75ea2a-f907-4994-ae5c-118632a1cb0f]
 description = "Non-existing codon can't translate"
 
 [9eac93f3-627a-4c90-8653-6d0a0595bc6f]
 description = "Unknown amino acids, not part of a codon, can't translate"
+reimplements = "1e75ea2a-f907-4994-ae5c-118632a1cb0f"
 
 [9d73899f-e68e-4291-b1e2-7bf87c00f024]
 description = "Incomplete RNA sequence can't translate"

exercises/practice/protein-translation/protein-translation-test.arr

@@ -164,9 +164,9 @@ fun stop-in-middle-of-six-codons():
   end
 end
 
-fun non-existent-codon():
-  check "Non-existing codon can't translate":
-    proteins("AAA") raises "Invalid codon"
+fun sequence-of-two-non-stop-codons():
+  check "Sequence of two non-STOP codons does not translate to a STOP codon":
+    proteins("AUGAUG") is [list: "Methionine", "Methionine"]
   end
 end
 
@@ -223,7 +223,7 @@ data TestRun: test(run, active) end
   test(stop-at-end-of-three-codons, false),
   test(stop-in-middle-of-three-codons, false),
   test(stop-in-middle-of-six-codons, false),
-  test(non-existent-codon, false),
+  test(sequence-of-two-non-stop-codons, false),
   test(unknown-codon, false),
   test(incomplete-sequence, false),
   test(incomplete-sequence-with-stop, false)

exercises/practice/protein-translation/protein-translation.arr

@@ -2,6 +2,54 @@ use context essentials2020 # Don't delete this line when using Pyret on Exercism
 
 provide: proteins end
 
+include string-dict
+import lists as L
+
+codon_mappings = [mutable-string-dict:
+  "AUG", "Methionine",
+  "UUU", "Phenylalanine",
+  "UUC", "Phenylalanine",
+  "UUA", "Leucine",
+  "UUG", "Leucine",
+  "UCU", "Serine",
+  "UCC", "Serine",
+  "UCA", "Serine",
+  "UCG", "Serine",
+  "UAU", "Tyrosine",
+  "UAC", "Tyrosine",
+  "UGU", "Cysteine",
+  "UGC", "Cysteine",
+  "UGG", "Tryptophan",
+  "UAA", "STOP",
+  "UAG", "STOP",
+  "UGA", "STOP"]
+
 fun proteins(strand):
-  raise("Please implement the proteins function")
+    proteins-recursive(string-explode(strand), [list: ])
+end
+
+fun proteins-recursive(current, acc):
+    ask:
+    | current.length() == 0 then: acc
+    | current.length() < 3 then: raise("Invalid codon")
+    | otherwise:
+      block:
+        codon = current.take(3).join-str("")
+        protein = translate-codon(codon)
+        ask:
+          | protein == "STOP" then: acc
+          | otherwise:
+            rest = split-at(3, current).suffix
+            L.append([list: protein], proteins-recursive(rest, acc))
+        end
+      end
+    end
+end
+
+
+fun translate-codon(codon):
+  cases(Option) codon_mappings.get-now(codon):
+    | some(a) => a
+    | none => raise("Invalid codon")
+  end
 end