attribute parser

[romainfrancois]

we need an R function that parses attributes from a file. Given a file, e.g.

...
// [[ foo::bar ]]
something

the function should return a list of data structures capturing:

• the attribute expression. Here the result of parse( text = "foo::bar" )
• the position in the file related to this particular attribute, i.e. right before the s of something.

[romainfrancois]

e.g.

> txt <- readLines( "/tmp/test.cpp")
> rx <- "^//[[:space:]]*[[][[](.*)[]][]].*"
> where <- grep( rx, txt )
> parse( text = gsub( rx, "\\1", txt[where] ) )
expression(Rcpp::export)

[kevinushey]

Implemented something that returns a list, with components:

• string: The actual line of code,
• code: The code within the // [[...]] attribute,
• expr: The code parsed as an R expression,
• index: The line number where the attribute was found,
• file: The file name.

[romainfrancois]

I have something too that i cooked up in the train. Sounds similar to what you have but it does some predispatch on the "type" of attribute:

• symbol
• negated symbol, i.e something like !debug
• call: e.g : foo(...)
• scoped call: bar::foo(...)
• scoped symbol: e.g foo::bar

[romainfrancois]

I just also pushed my code. we'll decide later what to do.

[romainfrancois]

I simplified my initial code so that parse_attribute gives a list of things of class "call_attribute" or "assignment_attribute":

> parse_attributes( '/tmp/foo.cpp' )
$attributes
$attributes[[1]]
$file
[1] "/tmp/foo.cpp"

$line
[1] 5

$content
 [1] "#include <Rcpp.h>"      "using namespace Rcpp ;" ""
 [4] ""                       "// [[Rcpp::export]]"    "int foo(int a, "
 [7] "    int b = 22"         "    ){"                 "  return 2 ;"
[10] "}"                      ""

$name
[1] "Rcpp::export"

$param
NULL

attr(,"class")
[1] "call_attribute"

$r_code_chunks
NULL

So this needs the handler called "Rcpp::export" with no param. Not yet sure what a handler is, as it has to have different meaning in the case of sourceCpp and compileAttributes