Add elisp/rna-transcription

elisp/rna-transcription/README.md

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+# Rna Transcription
+
+Given a DNA strand, return its RNA complement (per RNA transcription).
+
+Both DNA and RNA strands are a sequence of nucleotides.
+
+The four nucleotides found in DNA are adenine (**A**), cytosine (**C**),
+guanine (**G**) and thymine (**T**).
+
+The four nucleotides found in RNA are adenine (**A**), cytosine (**C**),
+guanine (**G**) and uracil (**U**).
+
+Given a DNA strand, its transcribed RNA strand is formed by replacing
+each nucleotide with its complement:
+
+* `G` -> `C`
+* `C` -> `G`
+* `T` -> `A`
+* `A` -> `U`
+## Source
+
+Rosalind [http://rosalind.info/problems/rna](http://rosalind.info/problems/rna)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

elisp/rna-transcription/rna-transcription-test.el

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+;;; rna-transcription-test.el --- Tests for RNA Transcription (exercism)
+
+;;; Commentary:
+
+
+;;; Code:
+
+(require 'cl)
+
+(load-file "rna-transcription.el")
+
+(ert-deftest transcribes-cytosine-to-guanine ()
+  (should (string= "G" (to-rna "C"))))
+
+(ert-deftest transcribes-guanine-to-cytosine ()
+  (should (string= "C" (to-rna "G"))))
+
+(ert-deftest transcribes-adenine-to-uracil ()
+  (should (string= "U" (to-rna "A"))))
+
+(ert-deftest transcribes-thymine-to-adenine ()
+  (should (string= "A" (to-rna "T"))))
+
+(ert-deftest it-transcribes-all-nucleotides ()
+  (should (string= "UGCACCAGAAUU"
+                   (to-rna "ACGTGGTCTTAA"))))
+
+(ert-deftest it-validates-dna-strands ()
+  (should-error (to-rna "XCGFGGTDTTAA")))
+
+(provide 'rna-transcription-test)
+;;; rna-transcription-test.el ends here

elisp/rna-transcription/rna-transcription.el

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+;;; rna-transcription.el -- RNA Transcription (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+(provide 'rna-transcription)
+
+(defun transcribe (nucleotide)
+"Return the matching RNA pair for DNA NUCLEOTIDE."
+  (cond ((char-equal nucleotide ?C) "G")
+        ((char-equal nucleotide ?G) "C")
+        ((char-equal nucleotide ?A) "U")
+        ((char-equal nucleotide ?T) "A")
+        ((error "Unrecognized nucleotide"))))
+
+(defun to-rna (dna)
+"Transcribe a string representing DNA nucleotides.
+Return a string representing RNA nucleotides."
+  (cl-loop for nucleotide being the elements of dna
+           concat (transcribe nucleotide)))
+
+;;; rna-transcription.el ends here