Python/Javascript String Concatenation in R

plus_character.R

`+` <- function(e1, e2) {
  ## unary
  if (missing(e2)) return(e1)
  if (!is.na(suppressWarnings(as.numeric(e1))) & !is.na(suppressWarnings(as.numeric(e2)))) {
    ## both arguments numeric-like but characters
    return(base::`+`(as.numeric(e1), as.numeric(e2)))
  } else if ((is.character(e1) & is.na(suppressWarnings(as.numeric(e1)))) | 
             (is.character(e2) & is.na(suppressWarnings(as.numeric(e2))))) {
    ## at least one true character 
    return(paste0(e1, e2))
  } else {
    ## both numeric
    return(base::`+`(e1, e2))
  }
}

"a" + "b"
#> [1] "ab"

"a" + 2
#> [1] "a2"

  2 + 2
#> [1] 4

  2 + "a"
#> [1] "2a"

  "2" + "2"
#> [1] 4
  
"butter" + "fly"
#> [1] "butterfly"

"susan" + "album" + "party"
#> [1] "susanalbumparty"

2 + "edgy" + 4 + "me"
#> [1] "2edgy4me"

+ 1
#> [1] 1

+ "a"
#> [1] "a"

Because this is a binary function acting left-to-right, the paste will only start as soon as a character is encountered, so

"tit" + 2 + 2 + "tat"
#> [1] "tit22tat"

but

2 + 2 + "crazy"
#> [1] "4crazy"