! Copyright (C) 2010 Benjamin Meinl.
! See http://factorcode.org/license.txt for BSD license.

! Library to calculate your average grade

USING: kernel io prettyprint namespaces math.parser sequences
    math ;
IN: average-grade

SYMBOL: grades

: init ( -- )
    V{ } clone grades set ;

: read-number ( -- number/f )
    readln string>number ;

: read-grades ( -- )
    [
        read-number dup [ grades get push ] when*
    ] loop ;

: average ( seq -- avg )
    [ sum ] [ length ] bi /f ;

: average-grade ( -- avg )
    grades get average ;

: main ( -- )
    "Enter grades, or nothing to stop:" print
    init read-grades average-grade . ;

MAIN: main