Re: [Rd] Contract Syntactic Sugar
Ivo,
Have you looked at the
TypeInfohttp://www.bioconductor.org/packages/2.12/bioc/html/TypeInfo.htmlBioConductor
package by Gentleman and Temple Lang?
I don't use it myself and can't speak to its current state, but from its
description, and having talked to one of its authors (who, for full
disclosure, is my advisor), it attempts to do what you want.
Also, as an aside, :: already means something else in R so I'm not sure
that particular sugar would work well.
~G
On Mon, Feb 4, 2013 at 1:53 PM, ivo welch ivo.we...@anderson.ucla.eduwrote:
## the following is a dream: add some sugar syntax to allow for
contracts with teeth (in and out checking)
is.positive - function(x) (all(x0))
exponentiate - function( x ::is.data.frame , exponent ::is.numeric
is.positive) :: is.vector is.numeric {
x$base :: is.positive## error also if base does not exist
in x; may need some special IQ
x$base^exponent
}
should be self-explanatory. anything that has '::' means run what is
before through all the functions after and barf if it is not true.
any other operator rather than :: or other syntax would be as
good---this is just illustratory. in the end, this code should be
viewed by R as the same as
exponentiate - function( x, exponent ) {
stopifnot( is.data.frame(x) )
stopifnot( is.numeric(exponent) )
stopifnot( is.positive(exponent) )
stopifnot( exists(base, x) )
stopifnot( is.positive( x$base ) )
return.value - x$base^exponent
stopifnot( is.vector(return.value) )
stopifnot( is.numeric(return.value) )
return.value
}
is this a feasible summer project for a student with a prospect of
inclusion of the completed code in the R core language itself if I pay
for the development time? {or does better syntax already exist and I
am just ignorant (which I often am)?}
regards,
/iaw
Ivo Welch (ivo.we...@gmail.com)
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--
Gabriel Becker
Graduate Student
Statistics Department
University of California, Davis
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Re: [Rd] Contract Syntactic Sugar
Ivo,
You might be interested in my lambda.r package which provides syntax (using the
%::% operator) for type constraints. Given a function with n arguments, the
type constraint requires n + 1 types, as the last type listed is the return
type. Lambda.r also provides syntax for specifying any arbitrary condition on
the input arguments via the %when% operator. For your example below you could
do the following:
exponentiate(x, exponent) %::% data.frame : numeric : numeric
exponentiate(x, exponent) %when% {
is.positive(x)
} %as% {
x$base ^ exponent
}
You can see more examples in the package (available on CRAN) or in the source
(https://github.com/muxspace/lambda.r).
HTH,
Brian
On Feb 4, 2013, at 4:53 PM, ivo welch ivo.we...@anderson.ucla.edu wrote:
## the following is a dream: add some sugar syntax to allow for
contracts with teeth (in and out checking)
is.positive - function(x) (all(x0))
exponentiate - function( x ::is.data.frame , exponent ::is.numeric
is.positive) :: is.vector is.numeric {
x$base :: is.positive## error also if base does not exist
in x; may need some special IQ
x$base^exponent
}
should be self-explanatory. anything that has '::' means run what is
before through all the functions after and barf if it is not true.
any other operator rather than :: or other syntax would be as
good---this is just illustratory. in the end, this code should be
viewed by R as the same as
exponentiate - function( x, exponent ) {
stopifnot( is.data.frame(x) )
stopifnot( is.numeric(exponent) )
stopifnot( is.positive(exponent) )
stopifnot( exists(base, x) )
stopifnot( is.positive( x$base ) )
return.value - x$base^exponent
stopifnot( is.vector(return.value) )
stopifnot( is.numeric(return.value) )
return.value
}
is this a feasible summer project for a student with a prospect of
inclusion of the completed code in the R core language itself if I pay
for the development time? {or does better syntax already exist and I
am just ignorant (which I often am)?}
regards,
/iaw
Ivo Welch (ivo.we...@gmail.com)
__
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Re: [Rd] Contract Syntactic Sugar
hi brian---interesting and very impressive. is it possible to move
everything into one definition and/or to chain multiple conditions?
exponentiate(x, exponent) %::% data.frame : c(numeric,allpositive) :
integer %as% {
x %has% base ## my invention, since this is not checked, and R is
not strict enough
x$base %::% allpositive
x$base ^ exponent
}
multiple creations as in your doc examples on the same function are a
recipe for errors for me. it's also why I am not too fond of
TypeInfo. chaining conditions in my c() is not important, as long as
I can define my own types (which can check multiple aspects at the
same time). suggestion: in your doc example, can you define a
different type than an integer? it's a little confusing. how about
defining a strictly positive integer?
regards,
/iaw
Ivo Welch (ivo.we...@gmail.com)
http://www.ivo-welch.info/
J. Fred Weston Professor of Finance
Anderson School at UCLA, C519
Director, UCLA Anderson Fink Center for Finance and Investments
Free Finance Textbook, http://book.ivo-welch.info/
Editor, Critical Finance Review, http://www.critical-finance-review.org/
On Mon, Feb 4, 2013 at 2:10 PM, Brian Lee Yung Rowe r...@muxspace.com wrote:
Ivo,
You might be interested in my lambda.r package which provides syntax (using
the %::% operator) for type constraints. Given a function with n arguments,
the type constraint requires n + 1 types, as the last type listed is the
return type. Lambda.r also provides syntax for specifying any arbitrary
condition on the input arguments via the %when% operator. For your example
below you could do the following:
exponentiate(x, exponent) %::% data.frame : numeric : numeric
exponentiate(x, exponent) %when% {
is.positive(x)
} %as% {
x$base ^ exponent
}
You can see more examples in the package (available on CRAN) or in the source
(https://github.com/muxspace/lambda.r).
HTH,
Brian
On Feb 4, 2013, at 4:53 PM, ivo welch ivo.we...@anderson.ucla.edu wrote:
## the following is a dream: add some sugar syntax to allow for
contracts with teeth (in and out checking)
is.positive - function(x) (all(x0))
exponentiate - function( x ::is.data.frame , exponent ::is.numeric
is.positive) :: is.vector is.numeric {
x$base :: is.positive## error also if base does not exist
in x; may need some special IQ
x$base^exponent
}
should be self-explanatory. anything that has '::' means run what is
before through all the functions after and barf if it is not true.
any other operator rather than :: or other syntax would be as
good---this is just illustratory. in the end, this code should be
viewed by R as the same as
exponentiate - function( x, exponent ) {
stopifnot( is.data.frame(x) )
stopifnot( is.numeric(exponent) )
stopifnot( is.positive(exponent) )
stopifnot( exists(base, x) )
stopifnot( is.positive( x$base ) )
return.value - x$base^exponent
stopifnot( is.vector(return.value) )
stopifnot( is.numeric(return.value) )
return.value
}
is this a feasible summer project for a student with a prospect of
inclusion of the completed code in the R core language itself if I pay
for the development time? {or does better syntax already exist and I
am just ignorant (which I often am)?}
regards,
/iaw
Ivo Welch (ivo.we...@gmail.com)
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R-devel@r-project.org mailing list
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Re: [Rd] Contract Syntactic Sugar
Ivo,
If you don't like the multipart function syntax you can write a single
definition. Personally I prefer this as it isolates data management logic and
control flow from model/application logic. There are duck typing operators that
you can use in the guard similar to the syntax you wrote. You can also create
your own types and use that in a type constraint. However the type constraint
syntax must be a distinct statement although you could embed it all within a
guard. Here are three different approaches using lambda.r.
NaturalNumber(x) %when% {
all(is.positive(x))
} %as% { x }
# Using an explicit type constraint with a custom type
exponentiate(x, exponent) %::% data.frame : NaturalNumber : integer
exponentiate(x, exponent) %when% {
x %hasa% base
} %as% { x$base ^ exponent }
-- or --
# Embedding everything in a guard
exponentiate(x, exponent) %when% {
x %hasa% base
x %isa% NaturalNumber
} %as% { x$base ^ exponent }
-- or --
# Eschewing a custom type for explicit statements
exponentiate(x, exponent) %when% {
x %hasa% base
all(is.positive(x$base))
} %as% { x$base ^ exponent
Warm Regards,
Brian
•
Brian Lee Yung Rowe
917 496 4583
On Feb 4, 2013, at 6:23 PM, ivo welch ivo.we...@gmail.com wrote:
hi brian---interesting and very impressive. is it possible to move
everything into one definition and/or to chain multiple conditions?
exponentiate(x, exponent) %::% data.frame : c(numeric,allpositive) :
integer %as% {
x %has% base ## my invention, since this is not checked, and R is
not strict enough
x$base %::% allpositive
x$base ^ exponent
}
multiple creations as in your doc examples on the same function are a
recipe for errors for me. it's also why I am not too fond of
TypeInfo. chaining conditions in my c() is not important, as long as
I can define my own types (which can check multiple aspects at the
same time). suggestion: in your doc example, can you define a
different type than an integer? it's a little confusing. how about
defining a strictly positive integer?
regards,
/iaw
Ivo Welch (ivo.we...@gmail.com)
http://www.ivo-welch.info/
J. Fred Weston Professor of Finance
Anderson School at UCLA, C519
Director, UCLA Anderson Fink Center for Finance and Investments
Free Finance Textbook, http://book.ivo-welch.info/
Editor, Critical Finance Review, http://www.critical-finance-review.org/
On Mon, Feb 4, 2013 at 2:10 PM, Brian Lee Yung Rowe r...@muxspace.com wrote:
Ivo,
You might be interested in my lambda.r package which provides syntax (using
the %::% operator) for type constraints. Given a function with n arguments,
the type constraint requires n + 1 types, as the last type listed is the
return type. Lambda.r also provides syntax for specifying any arbitrary
condition on the input arguments via the %when% operator. For your example
below you could do the following:
exponentiate(x, exponent) %::% data.frame : numeric : numeric
exponentiate(x, exponent) %when% {
is.positive(x)
} %as% {
x$base ^ exponent
}
You can see more examples in the package (available on CRAN) or in the
source (https://github.com/muxspace/lambda.r).
HTH,
Brian
On Feb 4, 2013, at 4:53 PM, ivo welch ivo.we...@anderson.ucla.edu wrote:
## the following is a dream: add some sugar syntax to allow for
contracts with teeth (in and out checking)
is.positive - function(x) (all(x0))
exponentiate - function( x ::is.data.frame , exponent ::is.numeric
is.positive) :: is.vector is.numeric {
x$base :: is.positive## error also if base does not exist
in x; may need some special IQ
x$base^exponent
}
should be self-explanatory. anything that has '::' means run what is
before through all the functions after and barf if it is not true.
any other operator rather than :: or other syntax would be as
good---this is just illustratory. in the end, this code should be
viewed by R as the same as
exponentiate - function( x, exponent ) {
stopifnot( is.data.frame(x) )
stopifnot( is.numeric(exponent) )
stopifnot( is.positive(exponent) )
stopifnot( exists(base, x) )
stopifnot( is.positive( x$base ) )
return.value - x$base^exponent
stopifnot( is.vector(return.value) )
stopifnot( is.numeric(return.value) )
return.value
}
is this a feasible summer project for a student with a prospect of
inclusion of the completed code in the R core language itself if I pay
for the development time? {or does better syntax already exist and I
am just ignorant (which I often am)?}
regards,
/iaw
Ivo Welch (ivo.we...@gmail.com)
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