R/is.R

In cyclotomic: The Field of Cyclotomic Numbers

isString <- function(x) {
  is.character(x) && length(x) == 1L && !is.na(x)
}

isInteger <- function(x) {
  is.numeric(x) && length(x) == 1L && !is.na(x) && as.integer(x) == x
}

isPositiveInteger <- function(x) {
  is.numeric(x) && length(x) == 1L && !is.na(x) && floor(x) == x
}

isStrictlyPositiveInteger <- function(x) {
  is.numeric(x) && length(x) == 1L && !is.na(x) && floor(x) == x && x != 0
}

isFraction <- function(x) {
  if(!isString(x)) {
    return(FALSE)
  }
  x <- trimws(x)
  if(grepl("^\\-*\\d+$", x)) {
    return(TRUE)
  }
  nd <- trimws(strsplit(x, "/")[[1L]])
  if(length(nd) != 2L) {
    FALSE
  } else {
    n <- nd[1L]
    if(!grepl("^\\-*\\d+$", n)) {
      FALSE
    } else {
      d <- nd[2L]
      if(!grepl("^\\d+$", d) || grepl("^0+$", d)) {
        FALSE
      } else {
        TRUE
      }
    }
  }
}