Instructions

Test suite

Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

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

Submitting Incomplete Solutions

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

rna-transcription-test.scm

;; Load SRFI-64 lightweight testing specification
(use-modules (srfi srfi-64))

;; Suppress log file output. To write logs, comment out the following line:
(module-define! (resolve-module '(srfi srfi-64)) 'test-log-to-file #f)

(add-to-load-path (dirname (current-filename)))
(use-modules (dna))

(test-begin "rna-transcription")

(test-equal "transcribes-cytosine-to-guanine"
          "G"
          (to-rna "C"))

(test-equal "transcribes-guanine-to-cytosine"
          "C"
          (to-rna "G"))

(test-equal "transcribes-adenine-to-uracil"
          "U"
          (to-rna "A"))

(test-equal "transcribes-thymine-to-adenine"
          "A"
          (to-rna "T"))

(test-equal "transcribes-all-nucleotides"
          "UGCACCAGAAUU"
          (to-rna "ACGTGGTCTTAA"))


(test-error "it-validates-dna-strands"
            #t
            (to-rna "XCGFGGTDTTAA"))

(test-end "rna-transcription")

(define-module (dna)
  #:export (to-rna))

(define (dna-to-rna dna)
  (cond
    ((char=? dna #\G) #\C)
    ((char=? dna #\C) #\G)
    ((char=? dna #\T) #\A)
    ((char=? dna #\A) #\U)))

(define (to-rna strand)
  (list->string 
    (map dna-to-rna 
      (string->list strand))))

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