| parse {base} | R Documentation |
parse returns the parsed but unevaluated expressions in a
list.
parse(file = "", n = NULL, text = NULL, prompt = "?", srcfile,
encoding = "unknown")
file |
a connection, or a character string giving the name of a
file or a URL to read the expressions from.
If |
n |
integer (or coerced to integer). The maximum number of
expressions to parse. If |
text |
character vector. The text to parse. Elements are treated as if they were lines of a file. Other R objects will be coerced to character if possible. |
prompt |
the prompt to print when parsing from the keyboard.
|
srcfile |
|
encoding |
encoding to be assumed for input strings. If the
value is |
If text has length greater than zero (after coercion) it is used in
preference to file.
All versions of R accept input from a connection with end of line marked by LF (as used on Unix), CRLF (as used on DOS/Windows) or CR (as used on classic Mac OS). The final line can be incomplete, that is missing the final EOL marker.
See source for the limits on the size of functions
that can be parsed (by default).
When input is taken from the console, n = NULL is equivalent to
n = 1, and n < 0 will read until an EOF character is
read. (The EOF character is Ctrl-Z for the Windows front-ends.) The
line-length limit is 4095 bytes when reading from the console (which
may impose a lower limit: see ‘An Introduction to R’).
The default for srcfile is set as follows. If
options("keep.source") is FALSE, srcfile
defaults to NULL. Otherwise, if text is used,
srcfile will be set to a srcfilecopy containing
the text. If a character string is used for file, a
srcfile object referring to that file will be used.
An object of type "expression", with up to n
elements if specified as a non-negative integer.
When srcfile is non-NULL, a "srcref" attribute
will be attached to the result containing a list of
srcref records corresponding to each element, a
"srcfile" attribute will be attached containing a copy of
srcfile, and a "wholeSrcref" attribute will be
attached containing a srcref record corresponding to
all of the parsed text.
A syntax error (including an incomplete expression) will throw an error.
Character strings in the result will have a declared encoding if
encoding is "latin1" or "UTF-8", or if
text is supplied with every element of known encoding in a
Latin-1 or UTF-8 locale.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
cat("x <- c(1,4)\n x ^ 3 -10 ; outer(1:7,5:9)\n", file="xyz.Rdmped")
# parse 3 statements from the file "xyz.Rdmped"
parse(file = "xyz.Rdmped", n = 3)
unlink("xyz.Rdmped")