Match params

Much like base::match.arg() with a few key differences:

• Will not perform partial matching

• Will not return error messages with ugly quotation marks

Usage

match_param(
  param,
  choices,
  null = TRUE,
  partial = getOption("mark.match_param.partial", FALSE),
  multiple = FALSE,
  simplify = TRUE
)

Arguments

param

The parameter

choices

The available choices; named lists will return the name (a character) for when matched to the value within the list element. A list of formula objects (preferred) retains the LHS of the formula as the return value when matched to the RHS of the formula.

null

If TRUE allows NULL to be passed a param

partial

If TRUE allows partial matching via base::pmatch()

multiple

If TRUE allows multiple values to be returned

simplify

If TRUE will simplify the output to a single value

Value

A single value from param matched on choices

Details

Param matching for an argument

Conditions

Conditions are generated through the {cnd} package. The following conditions are associated with this function:

mark:match_param_error/error

For more conditions, see: mark-cnd-conditions

See also

match_arg()

Examples

fruits <- function(x = c("apple", "banana", "orange")) {
  match_param(x)
}

fruits()         # apple
#> [1] "apple"
try(fruits("b")) # must be exact fruits("banana")
#> Error in match_param() : <mark:match_param_error>
#> `match_param(x)` failed in `fruits("b")`:
#>   param    b
#>   choices  apple, banana, orange
#> 
#> See exports for more help:
#>   ?mark::match_param

pfruits <- function(x = c("apple", "apricot", "banana")) {
  match_param(x, partial = TRUE)
}
pfruits()          # apple
#> [1] "apple"
try(pfruits("ap")) # matchParamMatchError
#> Error in match_param() : <mark:match_param_error>
#> `match_param(x)` failed in `pfruits("ap")`:
#>   param    ap
#>   choices  apple, apricot, banana
#> 
#> See exports for more help:
#>   ?mark::match_param
pfruits("app")     # apple
#> [1] "apple"

afruits <- function(x = c("apple", "banana", "orange")) {
  match_param(x, multiple = TRUE)
}

afruits() # apple, banana, orange
#> [1] "apple"  "banana" "orange"

# can have multiple responses
how_much <- function(x = list(too_few = 0:2, ok = 3:5, too_many = 6:10)) {
  match_param(x)
}

how_much(1)
#> [1] "too_few"
how_much(3)
#> [1] "ok"
how_much(9)
#> [1] "too_many"

# use a list of formulas instead
ls <- list(1L ~ 0:1, 2L, 3L ~ 3:5)
sapply(0:5, match_param, choices = ls)
#> [1] 1 1 2 3 3 3