R: Parse Expressions

parse {base}

R Documentation

Parse Expressions

Description

parse returns the parsed but unevaluated expressions in a list. Each element of the list is of mode expression.

Usage

parse(file = "", n = NULL, text = NULL, prompt = "?", white = FALSE)

Arguments

file

a connection, or a character string giving the name of a file or a URL to read the expressions from. If file is "" and text is missing or NULL then input is taken from the console.

n

the number of statements to parse. If n is negative the file is parsed in its entirety.

text

character vector. The text to parse. Elements are treated as if they were lines of a file.

prompt

the prompt to print when parsing from the keyboard. NULL means to use R's prompt, options("prompt")[[1]].

white

if TRUE then any white space separates expressions otherwise only newlines or semicolons do.

Details

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 Mac). 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).

Examples

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")