how to count number of letters with std.algorithm.count / std.algorithm.reduce / std.algorithm.map ?

[bioinfornatics]

hi,

I would like to count number of one ore more letter into a string 
or list of string (string[]) without use a for loop but instead 
using std.algorithm to compute efficiently.

if you have:
  string   seq1 = "ACGATCGATCGATCGCGCTAGCTAGCTAG";
  string[] seq2 = ["ACGATCGATCGATCGCGCTAGCTAGCTAG", 
"ACGATGACGATCGATGCTAGCTAG"];

i try :

reduce!( (seq) => seq.count("G"), 
seq.count("C"))(tuple(0LU,0LU),seq1)

and got:
Error: undefined identifier seq, did you mean import std?

in morre count seem to request a range then to do multiple count 
into one string it is not easy.

Thanks to show to me how do this

Regards