Problem Statement

In bioinformatics, long character strings are often encoded in a format called FASTA.
A FASTA file can contain several strings, each identified by a name marked by a > (greater than) character at the beginning of the line.

Write a program that reads a FASTA file such as: Note that a high-quality implementation will not hold the entire file in memory at once; real FASTA files can be multiple gigabytes in size.

Let's start with the solution:

USING: formatting io kernel sequences ;
IN: rosetta-code.fasta

: process-fasta-line ( str -- )
    dup ">" head? [ rest "\n%s: " printf ] [ write ] if ;

: main ( -- )
    readln rest "%s: " printf [ process-fasta-line ] each-line ;

MAIN: main