srcfile {base} | R Documentation |
These functions are for working with source files.
srcfile(filename, encoding = getOption("encoding"), Enc = "unknown") srcfilecopy(filename, lines) getSrcLines(srcfile, first, last) srcref(srcfile, lloc) ## S3 method for class 'srcfile': print(x, ...) ## S3 method for class 'srcfile': summary(object, ...) ## 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': summary(object, useSource = FALSE, ...) ## S3 method for class 'srcref': as.character(x, useSource = TRUE, ...) .isOpen(srcfile)
filename |
The name of a file |
encoding |
The character encoding to assume for the file |
Enc |
The encoding with which to make strings: see the
encoding argument of parse . |
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 or six values giving a source location; see ‘Details’. |
x, object, con |
An object of the appropriate class. |
useSource |
Whether to read the srcfile to obtain the
text of a srcref . |
... |
Additional arguments to the methods; these will be ignored. |
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_byte, last_line, last_byte, first_column,
last_column)
. (Bytes and columns may be different due to multibyte
characters. If only four values are given, the columns and
bytes are assumed to match.)
Methods are defined for print
, summary
, 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
, summary
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. The
summary
method defaults to this type of display.
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.
srcfile
returns a srcfile
object.
srcfilecopy
returns a srcfilecopy
object.
getSrcLines
returns a character vector of source code lines.
srcref
returns a srcref
object.
Duncan Murdoch
src <- srcfile(system.file("DESCRIPTION", package = "base")) summary(src) getSrcLines(src, 1, 4) ref <- srcref(src, c(1, 1, 2, 1000)) ref print(ref, useSource = FALSE)