RosettaCodeData/Task/Cumulative-standard-deviation/Factor/cumulative-standard-deviati...

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635 B
Factor

USING: accessors io kernel math math.functions math.parser
sequences ;
IN: standard-deviator
TUPLE: standard-deviator sum sum^2 n ;
: <standard-deviator> ( -- standard-deviator )
0.0 0.0 0 standard-deviator boa ;
: current-std ( standard-deviator -- std )
[ [ sum^2>> ] [ n>> ] bi / ]
[ [ sum>> ] [ n>> ] bi / sq ] bi - sqrt ;
: add-value ( value standard-deviator -- )
[ nip [ 1 + ] change-n drop ]
[ [ + ] change-sum drop ]
[ [ [ sq ] dip + ] change-sum^2 drop ] 2tri ;
: main ( -- )
{ 2 4 4 4 5 5 7 9 }
<standard-deviator> [ [ add-value ] curry each ] keep
current-std number>string print ;