srcfile {base}

R Documentation

References to source files

Description

These functions are for working with source files.

Usage

srcfile(filename, encoding = getOption("encoding"))
srcfilecopy(filename, lines)
getSrcLines(srcfile, first, last)
srcref(srcfile, lloc)
## S3 method for class 'srcfile'
print(x, ...)
## S3 method for class 'srcfile'
open(con, line, ...)
## S3 method for class 'srcfile'
close(con, ...)
## S3 method for class 'srcref'
print(x, useSource = TRUE, ...)
## S3 method for class 'srcref'
as.character(x, useSource = TRUE, ...)
.isOpen(srcfile)

Arguments

filename	The name of a file
encoding	The character encoding to assume for the file
lines	A character vector of source lines. Other R objects will be coerced to character.
srcfile	A srcfile object.
first, last, line	Line numbers.
lloc	A vector of four values giving a source location; see ‘Details’.
x, con	An object of the appropriate type.
useSource	Whether to read the srcfile to obtain the text of a srcref.
...	Additional arguments to the methods; these will be ignored.

Details

These functions and classes handle source code references.

The srcfile function produces an object of class srcfile, which contains the name and directory of a source code file, along with its timestamp, for use in source level debugging (not yet implemented) and source echoing. The encoding of the file is saved; see file for a discussion of encodings, and iconvlist for a list of allowable encodings on your platform.

The srcfilecopy function produces an object of the descendant class srcfilecopy, which saves the source lines in a character vector.

The getSrcLines function reads the specified lines from srcfile.

The srcref function produces an object of class srcref, which describes a range of characters in a srcfile. The lloc value gives the following values: c(first_line, first_column, last_line, last_column).

Methods are defined for print, open, and close for classes srcfile and srcfilecopy. The open method opens its internal file connection at a particular line; if it was already open, it will be repositioned to that line.

Methods are defined for print and as.character for class srcref. The as.character method will read the associated source file to obtain the text corresponding to the reference. If an error occurs (e.g. the file no longer exists), text like <srcref: "file" chars 1:1 to 2:10> will be returned instead, indicating the line:column ranges of the first and last character.

Lists of srcref objects may be attached to expressions as the "srcref" attribute. (The list of srcref objects should be the same length as the expression.) By default, expressions are printed by print.default using the associated srcref. To see deparsed code instead, call print with argument useSource = FALSE. If a srcref object is printed with useSource = FALSE, the <srcref: ...> record will be printed.

.isOpen is intended for internal use: it checks whether the connection associated with a srcfile object is open.

Value

srcfile returns a srcfile object.

srcfilecopy returns a srcfilecopy object.

getSrcLines returns a character vector of source code lines.

srcref returns a srcref object.

Author(s)

Duncan Murdoch

Examples

src <- srcfile(system.file("DESCRIPTION", package = "base"))
getSrcLines(src, 1, 4)
ref <- srcref(src, c(1, 1, 2, 1000))
ref
print(ref, useSource = FALSE)

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