Curry: proposed new functional programming, er, function.

Hi,
On 04/05/2011 10:40 AM, Ravi Varadhan wrote:
I too would like this (being an Indian!).

Here is an example that came up just yesterday with regards to solving a
quadrature problem using the "cubature" package. ?The adaptIntegrate
function does not allow additional arguments via ...

Uwe suggested a work around, but `Curry' would solve it nicely (and it
also tastes better!):

Curry = function(FUN,...) {
.orig = list(...)
function(...) do.call(FUN,c(.orig, list(...)))
}

require(cubature)

f<- function(x, a) cos(2*pi*x*a) ?# a simple test function

# this works
a<- 0.2
adaptIntegrate(function(x, argA=a) f(x, a=argA), lower=0, upper=2)

# but this doesn't work
rm(a)
adaptIntegrate(function(x, argA=a) f(x, a=argA), lower=0, upper=2, a=0.2)

# Use of Curry
adaptIntegrate(Curry(f, a=0.2), lower=0, upper=2)
Two objections:

1. ?I don't see how that is preferable to

adaptIntegrate(function(x) f(x, a=0.2), lower=0, upper=2)
In this particular case I don't think it is. The reason I proposed it
yesterday for the cubature example was that in some cases it can make
the code more concise and clearer in my opinion. This is the case when
you override a considerable number of arguments in a function.

Consider this,

read.table2 = Curry(read.table, header = TRUE, na.strings = "9999",
    colClasses = "numeric", nrows = 23)

vs

read.table2 = function(..., header = TRUE, na.strings = "9999",
    colClasses = "numeric", nrows = 23)
{
     read.table(header = header, na.strings = na.strings,
       colClasses = colClasses, nrows = nrows, ...)
}

Whether or not this should be called curry, I have no idea. In any
case it seems like a useful function to have in a base package,
regardless of its implementation details.

baptiste
2. ?There seems to be confusion about what currying means. ?The Wikipedia
page <http://en.wikipedia.org/wiki/Currying> indicates that the function
Curry() defined above is really doing "partial function application", not
currying. ?I'm in no position to judge whether Byron got it right or
Wikipedia did, but this suggests to me that the name "Curry" is
inappropriate, since at least some people who know what currying is would
not guess that it does what it does.

Duncan Murdoch

Best,
Ravi.

-------------------------------------------------------
Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology School of Medicine Johns
Hopkins University

Ph. (410) 502-2619
email: rvaradhan at jhmi.edu

-----Original Message-----
From: r-devel-bounces at r-project.org [mailto:r-devel-bounces at r-project.org]
On Behalf Of Hadley Wickham
Sent: Wednesday, May 04, 2011 10:29 AM
To: Byron Ellis
Cc: R Development Mailing List
Subject: Re: [Rd] Curry: proposed new functional programming, er,
function.

I thought I might bring this up again - it now seems like Curry would
be a natural fit with Reduce, Filter, Find, Map, Negate and Position.
Any chance we might see this in a future version of R?

Hadley

On Thu, Nov 1, 2007 at 2:00 PM, Byron Ellis<byron.ellis at gmail.com> ?wrote:
?Hi all (especially R-core) I suppose,

?With the introduction of the new functional programming functions into
?base I thought I'd ask for a Curry() function. I use a simple one that
?looks this:

?Curry = function(FUN,...) { .orig = list(...);function(...)
?do.call(FUN,c(.orig,list(...))) }

?This comes in really handy when using say, heatmap():

?heatmap(mydata,hclustfun=Curry(hclust,method="average"))

?or other functions where there are ... arguments, but it's not clear
?where they should end up.

?--
?Byron Ellis (byron.ellis at gmail.com)
?"Oook" -- The Librarian

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Curry: proposed new functional programming, er, function.

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