GENERIC: next-value ( generator -- value )

! Sine generator

TUPLE: sine-generator amplitude current delta ;
: <sine-generator> ( amplitude freq -- sine-generator ) 2 pi * swap / [ pi ] dip sine-generator boa ;
M: sine-generator next-value 
    [ current>> sin ]
    [ amplitude>> ]
    [ dup
        [ current>> ] [ delta>> ] bi + 
        dup 2 pi * >= [ 2 pi * - ] when
    >>current drop ] tri * ;


: sine-data ( samples sample-rate amplitude freq -- byte-array )
    pick swap /
    <sine-generator>
    [ drop 0 <array> ] dip
    [ next-value nip ] curry map ;