Paccum : Pattern

An accumulator -- repeatedly performs a binary operation on the previous stream value and the result of a second stream. Each output value becomes the input value for the next calculation.

Where Pseries adds a constant value on successive iterations, here the second operand is variable.

*new(lo = -inf, hi = inf, step, length = inf, start, operator = '+')

lo = minimum output value; values lower than this are .fold-ed back in range

hi = maximum output value

step = pattern for the second operand

length = number of values to output

start = starting value; if not given, the stream will start with rrand(lo, hi)

operator = by default, '+'; you may use other operators. This may be a pattern to do different operations per iteration.

Examples:

p = Pseries(0, 1, inf).asStream;

p.nextN(10);

[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]

p = Paccum(step: 1, length: inf, start: 0).asStream;

p.nextN(10);

[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]

p = Paccum(step: Pwhite(1, 5, inf), length: inf, start: 0).asStream;

p.nextN(10);

[ 0, 4, 8, 10, 11, 14, 17, 18, 23, 25 ]

p = Paccum(step: Pwhite(1, 5, inf), length: inf, start: 200, operator: '/').asStream;

p.nextN(10);

[ 200, 100, 20, 10, 2, 1, 1, 0.33333333333333, 0.16666666666667, 0.033333333333333 ]