dna.nim

import algorithm

# Complementing a strand of DNA
# I want to reverse the string "s" and then replace
# all A's with T's
# all T's with A's
# all C's with G's
# all G's with C's

# define my string variable
var s: string = "AAACCCGGT"

# reverse my string variable
reverse(s)

proc replaceInplace(s: var string) =
  for c in s.mitems:
    case c
    of 'A': c = 'T'
    of 'C': c = 'G'
    of 'G': c = 'C'
    of 'T': c = 'A'
    else: discard
    
proc replaceInplace2(s: var string) =
  for i, c in s:
    case c
    of 'A': s[i] = 'T'
    of 'C': s[i] = 'G'
    of 'G': s[i] = 'C'
    of 'T': s[i] = 'A'
    else: discard

# replace all my letters
replaceInplace(s)

# print out result
echo s