How can I apply list of functions consecutively to a variable?

Question

I have a list of functions I want to apply to a string consecutively, changing the string. For example, a list of regular expressions I want to remove from a string, e.g.

to_remove = c('a','b')
original = 'abcabd'

In this case, I could use a simple regular expression, e.g. 'a|b'.

library(stringr)
str_remove( original, paste0( to_remove, collapse='|'))

The actual situation is more complex than this, and the regular expression gets a little hairy. Also, I am curious how to do this in a proper R way.

Another way to phrase the question is, "How can I implement the following for loop using a vector approach?"

for( rem in to_remove) {
      original = str_remove( original, rem )
}

'

Answer 1

stringi offers vectorized string replacement. The replacement argument can take on a vector of length 1, "", or a vector of the same length.

to_remove = c('a','b')
original = 'abcabd'

stringi::stri_replace_all_fixed(
    str = original,
    pattern = to_remove,
    replacement = "",
    vectorize_all = F
)
#> [1] "cd"

For repeated application of patterns, perhaps use an alternative pattern, per Stéphane's comment, replace_all_* with vectorize = FALSE is recursive, see for example the output of

stri_replace_all_regex(
    "abc", 
    pattern = c("^a", "^b"),
    replacement = "", 
    vectorise_all = FALSE
)
#> [1] "c"