Decorators in R

deco.R

deco <- function(f) {

  wrapper <- function(...) {
    # <code prior to execution>
    res <- f(...)
    # <code after execution>

    return(res)
  }

  return(wrapper)
}

deco2.R

deco <- function(f) {

  wrapper <- function(...) {
    # Optional: extract arguments
    args <- list(...)
    # <more code prior to execution>
    res <- f(unlist(args))
    # <code after execution>

    return(res)
  }

  return(wrapper)
}

log1starg.R

log1starg <- function(f, filename = 'loginput.txt') {

  wrapper <- function(x, ...) {
    # Before execution
    write(x, file = filename, append = TRUE) # Log the first argument only
    
    res <- f(x, ...)

    return(res)
  }
  
  return(wrapper)
}

logger.R

logger <- function(f, filename = 'log.txt') {

  wrapper <- function(...) {
    # Before execution
    # Do nothing

    res <- f(...)

    # After execution
    write(res, file = filename, append = TRUE)

    return(res)
  }

  return(wrapper)
}

timer.R

timer <- function(f) {

  wrapper <- function(...) {
    # Before execution
    op <- options(digits.secs = 6) # Our example is fast. Increase time resolution
    print(paste("Ini time:", Sys.time())) # Show the clock before execution

    res <- f(...)

    # After execution
    print(paste("End time:", Sys.time())) # Show the clock after execution

    return(res)
  }

  return(wrapper)
}