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39 lines
1.4 KiB
Lua

local Observable = require "rx.observable"
local util = require "rx.util"
--- Returns a new Observable that produces a single value computed by accumulating the results of
-- running a function on each value produced by the original Observable.
-- @arg {function} accumulator - Accumulates the values of the original Observable. Will be passed
-- the return value of the last call as the first argument and the
-- current values as the rest of the arguments.
-- @arg {*} seed - A value to pass to the accumulator the first time it is run.
-- @returns {Observable}
function Observable:reduce(accumulator, seed)
return Observable.create(function(observer)
local result = seed
local first = true
local function onNext(...)
if first and seed == nil then
result = ...
first = false
else
return util.tryWithObserver(observer, function(...)
result = accumulator(result, ...)
end, ...)
end
end
local function onError(e)
return observer:onError(e)
end
local function onCompleted()
observer:onNext(result)
return observer:onCompleted()
end
return self:subscribe(onNext, onError, onCompleted)
end)
end