Parse formal arguments of functions

Parse formal arguments of functions and convert them to f_usage objects.

Usage

parse_pairlist(x)

pairlist2f_usage1(x, name, S3class = "", S4sig = "", infix = FALSE,
                  fu = TRUE)

Arguments

x: a pairlist representing the arguments of a function.
name: function name.
S3class: S3 class, see `Details'
S4sig: S4 signature, see Details.
infix: if TRUE the function usage is in infix form, see Details.
fu: if TRUE the object is a function, otherwise it is something else (e.g. a variable or a constant like pi and Inf).

Details

These functions are mostly internal.

parse_pairlist parses the pairlist object, x, into a list with two components. The first component contains the names of the arguments. The second component is a named list containing the default values, converted to strings. Only arguments with default values have entries in the second component (so, it may be of length zero). If x is empty or NULL, both components have length zero. An example: parse_pairlist(formals(system.file))

pairlist2f_usage1() creates an object of S3 class "f_usage". The object contains the result of parsing x with parse_pairlist(x) and a number of additional components which are copies of the remaining arguments to the function (without any processing). The components are listed in section Values. S3class is set to an S3 class for for S3 methods, S4sig is the signature of an S4 method (as used in Rd macro \S4method). infix is TRUE for the rare occations when the function is primarily used in infix form.

Class "f_usage" has a method for as.character() which generates a text suitable for inclusion in Rd documentation. pairlist2f_usage1(formals(summary.lm), "summary", S3class = "lm")

Value

For parse_pairlist, a list with the following components:

argnames: the names of all arguments, a character vector
defaults: a named character vector containing the default values, converted to character strings. Only arguments with defaults have entries in this vector.

For pairlist2f_usage1, an object with S3 class "f_usage". This is a list as for parse_pairlist and the following additional components:

name: function name, a character string.
S3class: S3 class, a character string; "" if not an S3 method.
S4sig: S4 signature; "" if not an S4 method.
infix: a logical value, TRUE for infix operators.
fu: indicates the type of the object, usually TRUE, see Details.

Author

Georgi N. Boshnakov

Examples

parse_pairlist(formals(lm))
#> $argnames
#>  [1] "formula"     "data"        "subset"      "weights"     "na.action"  
#>  [6] "method"      "model"       "x"           "y"           "qr"         
#> [11] "singular.ok" "contrasts"   "offset"      "..."        
#> 
#> $defaults
#>      method       model           x           y          qr singular.ok 
#>    "\"qr\""      "TRUE"     "FALSE"     "FALSE"      "TRUE"      "TRUE" 
#>   contrasts 
#>      "NULL" 
#> 
parse_pairlist(formals(system.file))
#> $argnames
#> [1] "..."      "package"  "lib.loc"  "mustWork"
#> 
#> $defaults
#>    package    lib.loc   mustWork 
#> "\"base\""     "NULL"    "FALSE" 
#> 
s_lm <- pairlist2f_usage1(formals(summary.lm), "summary", S3class = "lm")
s_lm
#> name      = summary 
#> S3class   = lm 
#> S4sig     =  
#> infix     = FALSE 
#> fu        = TRUE 
#> argnames  = object correlation symbolic.cor ... 
#> defaults  : correlation = FALSE 
#>             symbolic.cor = FALSE 
#> 
as.character(s_lm)
#>                                                                            summary 
#> "\\method{summary}{lm}(object, correlation = FALSE, symbolic.cor = FALSE, \\dots)"