Regular expression method dispatch and function application

The humdrumR regular-expression method dispatch system is a simple system for making new functions which can by smartly applied to a variety of character strings. Humdrum dispatch works like normal R method dispatch, but instead of dispatching specific methods based on their class (integer, character, etc.) it dispatches based on regular expressions. In addition, exclusive interpretations can be used to guide dispatch.

Usage

humdrumDispatch(
  x,
  dispatchDF,
  Exclusive = NULL,
  funcName = NULL,
  regexApply = TRUE,
  multiDispatch = FALSE,
  ...,
  outputClass = "character"
)

exclusiveDispatch(
  x,
  dispatchDF,
  Exclusive,
  regexApply = TRUE,
  outputClass = "character",
  inPlace = FALSE,
  ...
)

makeDispatchDF(...)

makeHumdrumDispatcher(
  ...,
  funcName = "humdrum-dispatch",
  outputClass = "character",
  args = alist(),
  memoize = TRUE,
  dispatch.attr = TRUE
)

# S3 method for humdrumDispatch
print(x)

Arguments

dispatchDF

A data.frame which describes what function should be called for which regex input. (See details).

Must be a data.frame.

Exclusive

Exclusive interpretations to dispatch.

Defaults to NULL.

If NULL, only the regexes are used for dispatch.

multiDispatch

Whether to use multiple dispatch function for each interpretation.

Defaults to FALSE.

Must be a singleton logical value: an on/off switch.

If FALSE the "best" regex/exclusive match is dispatched for each Exclusive segment. If TRUE, differenet functions can be dispatched within the same input vector.

...

Arguments to pass to dispatch functions.

outputClass

The default output class which the function should return.

Defaults to "character".

Must be single character string.

Generally, to make sense, all dispatched functions should return the same type, which you should explicitly indicate with the outputClass argument. Dispatch functions should also be vectorized.

str

The input strings, on which dispatch is called.

Must be character.

Details

Many humdrumR functions are in fact, humdrum-dispatch functions: for example, tonalInterval.character(). If you call tonalInterval('ee-'), the function will recognize that the input string is a token in the **kern representation, and call the appropriate parser. If you instead call tonalInterval('me'), the function will recognize that the input string is a token in the **solfa representation, and call the appropriate parser for that.

dispatchDF

The dispatchDF must be a data.table::data.table() created using the makeDispatchDF function. makeDispatchDF takes one or more arguments, each a list with three components (ordered, not nameed):

A character vector of exclusive interpretations. (Specify "any" if you don't want exclusive dispatch).
A regular expression (character string) or a function which can generate a regular expression, which accepts ... arguments at the time of dispatch.
A function to dispatch.

makeHumdrumDispatcher

makeHumdrumDispatcher is a function which creates a new function which automatically performs humdrum-dispatch. A number of important humdrumR functions are created with makeHumdrumDispatcher:

tonalInterval.character
diatonicSet.character
tertianSet.character
rhythmInterval.character

Examples


u <- c('A', 'B', 'CD', 'E', 'F', 'gh', 'L', 'KX')
l <- c('a', 'b', 'cd', 'e', 'f', 'gh', 'l', 'kx')

lowercasefunc <- \(x) 5L - nchar(x)

humdrumDispatch(l, outputClass = 'integer',
                makeDispatchDF(list('any', '[a-z]+',  lowercasefunc),
                               list('any', '[A-Z]+',  nchar)))
#> [1] 4 4 3 4 4 3 4 3
#> attr(,"dispatch")
#> attr(,"dispatch")$Original
#> [1] "a"  "b"  "cd" "e"  "f"  "gh" "l"  "kx"
#> 
#> attr(,"dispatch")$Regexes
#>   [a-z]+ 
#> "[a-z]+" 
#> 
#> attr(,"dispatch")$Segments
#> [1] 1
#> 
#> attr(,"dispatch")$Exclusives
#> [1] "any"
#> 
 # lowercasefunc will be called on l, nchar on u