Package 'scaffolder'

Custom Scaffolding of R Wrappers for Python Functions

Description

This function can be used to generate R wrapper for a specified Python function while allowing to inject custom code for critical parts of the wrapper generation, such as process the any part of the obtained docs and append additional roxygen fields. The result from execution of python_function is assigned to a variable called python_function_result that can also be processed by postprocess_fn before writing the closing curly braces for the generated wrapper function.

Usage

custom_scaffold_py_function_wrapper(
  python_function,
  r_function = NULL,
  additional_roxygen_fields = NULL,
  process_docs_fn = function(docs) docs,
  process_param_fn = function(param, docs) param,
  process_param_doc_fn = function(param_doc, docs) param_doc,
  postprocess_fn = NULL,
  file_name = NULL
)

Arguments

python_function	Fully qualified name of Python function or class constructor (e.g. tf$nn$top_k)
r_function	Name of R function to generate (defaults to name of Python function if not specified)
additional_roxygen_fields	A list of additional roxygen fields to write to the roxygen docs, e.g. list(export = "", rdname = "generated-wrappers").
process_docs_fn	A function to process the obtained docs.
process_param_fn	A function to process each parameter needed for python_funcion before executing python_funcion.
process_param_doc_fn	A function to process the roxygen docstring for each parameter.
postprocess_fn	A function to inject any custom code in the form of a string before writing the closing curly braces for the generated wrapper function.
file_name	The file name to write the generated wrapper function to. If NULL, the generated wrapper will only be printed out in the console.

Examples

library(tensorflow)
library(stringr)

# Example of a `process_param_fn` to cast parameters with default values
# that contains "L" to integers
process_int_param_fn <- function(param, docs) {
  # Extract the list of parameters that have integer values as default
  int_params <- gsub(
    " = [-]?[0-9]+L",
    "",
    str_extract_all(docs$signature, "[A-z]+ = [-]?[0-9]+L")[[1]])
  # Explicitly cast parameter in the list obtained above to integer
  if (param %in% int_params) {
    param <- paste0("as.integer(", param, ")")
  }
  param
}

# Note that since the default value of parameter `k` is `1L`. It is wrapped
# by `as.integer()` to ensure it's casted to integer before sending it to `tf$nn$top_k`
# for execution. We then print out the python function result.
custom_scaffold_py_function_wrapper(
  "tf$nn$top_k",
  r_function = "top_k",
  process_param_fn = process_int_param_fn,
  postprocess_fn = function() { "print(python_function_result)" })

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Scaffold R wrappers for Python functions

Description

Scaffold R wrappers for Python functions

Usage

scaffold_py_function_wrapper(
  python_function,
  r_function = NULL,
  file_name = NULL
)

Arguments

python_function	Fully qualified name of Python function or class constructor (e.g. tf$nn$top_k)
r_function	Name of R function to generate (defaults to name of Python function if not specified)
file_name	The file name to write the generated wrapper function to. If NULL, the generated wrapper will only be printed out in the console.

Note

The generated wrapper will often require additional editing (e.g. to convert Python list literals in the docs to R lists, to massage R numeric values to Python integers via as.integer where required, etc.) so is really intended as an starting point for an R wrapper rather than a wrapper that can be used without modification.

Examples

library(scaffolder)
library(tensorflow)

scaffold_py_function_wrapper("tf$nn$top_k")

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Scaffolding Interfaces to Packages in Other Programming Languages

Description

This package provides a comprehensive set of tools to scaffold interfaces to modules, classes, functions, and documentations written in other programming languages.

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