FunctionProducerConsumer-classes: Classes for user-defined Producers and Consumers
In Streamer: Enabling stream processing of large files

Description Usage Arguments Constructors Methods Internal Class Fields and Methods Author(s) See Also Examples

The FunctionProducer and FunctionConsumer classes provide an easy way to quickly create Producer and Consumer instances from user-provided functions.

1 2	FunctionProducer(FUN, RESET, ..., state=NULL) FunctionConsumer(FUN, RESET, ..., state=NULL)

`FUN`	User defined function to yield successive records in the stream. The `FunctionProducer` function must return an object of length 0 (e.g., `logical(0)`) when the stream is complete.
`RESET`	An optional function of one arugment (‘state’) to reset the stream to its original state. If missing, the stream cannot be reset.
`...`	Arguments passed to the `Producer`-class or `Consumer`-class constructors.
`state`	Any information, made available to `RESET`.

Use FunctionProducer or FunctionConsumer to construct instances of this class.

See Producer and Consumer Methods.

Internal fields of this class are are described with, e.g., getRefClass("FunctionProducer")$fields.

Internal methods of this class are described with getRefClass("FunctionProducer")$methods() and getRefClass("FunctionProducer")$help().

Nishant Gopalakrishnan ngopalak@fhcrc.org

Stream

## A ProducerFunction
producerFun <- function() 
    ## produce the mean of 10 random uniform numbers
    ## stop when the mean is greater than 0.8
{
    x <- mean(runif(10))
    if (x > .8) numeric(0) else x
}
randomSampleMeans <- FunctionProducer(producerFun)
result <- sapply(randomSampleMeans, c)
length(result)
head(result)

## A FunctionConsumer:
consumerFun <- function(y)
    ## transform input by -10 log10
{
    -10 * log10(y)
}

neg10log10 <- FunctionConsumer(consumerFun)

strm <- Stream(randomSampleMeans, neg10log10)
result <- sapply(strm, c)
length(result)
head(result)