diff --git a/R/basics.r b/R/basics.r
deleted file mode 100644
index 12d2cd49..00000000
--- a/R/basics.r
+++ /dev/null
@@ -1,144 +0,0 @@
-#' The length of a string (in characters).
-#'
-#' @param string input character vector
-#' @return numeric vector giving number of characters in each element of the 
-#'   character vector.  Missing string have missing length.
-#' @keywords character
-#' @seealso \code{\link{nchar}} which this function wraps
-#' @examples
-#' str_length(letters)
-#' str_length(c("i", "like", "programming", NA))
-str_length <- function(string) {
-  string <- as.character(string)
-  nc <- nchar(string)
-  is.na(nc) <- is.na(string)
-  nc
-}
-
-#' Join multiple strings into a single string.
-#' 
-#' @param ... one or more character vectors.  Zero length arguments 
-#'   are removed
-#' @param sep string to insert between input vectors
-#' @param collapse optional string used to combine input vectors into single
-#'   string
-#' @return If \code{collapse = NULL} (the default) a character vector with 
-#'   length equal to the longest input string.  If \code{collapse} is non-
-#'   NULL, a character vector of length 1.
-#' @keywords character
-#' @seealso \code{\link{paste}} which this function wraps
-#' @examples
-#' str_join("Letter: ", letters)
-#' str_join("Letter", letters, sep = ": ")
-#' str_join(letters, " is for", "...")
-#' str_join(letters[-26], " comes before ", letters[-1])
-#'
-#' str_join(letters, collapse = "")
-#' str_join(letters, collapse = ", ")
-str_join <- function(..., sep = "", collapse = NULL) {
-  strings <- Filter(function(x) length(x) > 0, list(...))
-  
-  do.call("paste", c(strings, list(sep = sep, collapse = collapse)))
-}
-
-#' Trim whitespace from start and end of string.
-#' 
-#' @param string input character vector
-#' @return character vector with leading and trailing whitespace removed
-#' @keywords character
-#' @examples
-#' str_trim("  String with trailing and leading white space\t")
-#' str_trim("\n\nString with trailing and leading white space\n\n")
-str_trim <- function(string) {
-  str_replace(string, "^\\s+|\\s+$", "")
-}
-
-#' Extract substrings from a character vector.
-#'
-#' \code{sub_str} will replicate all arguments to be the same length as the 
-#' longest argument.  If any arguments are of length 0, the output will be 
-#' a zero length character vector.
-#'
-#' @param string input character vector
-#' @param start integer vector giving position of first charater in substring, 
-#'   defaults to first character.
-#' @param end integer vector giving position of last character in substring, 
-#'   defaults to last character.
-#' @return character vector of substring.  Will be length of longest input
-#'   argument
-#' @keywords character
-#' @seealso \code{\link{substring}} which this function wraps
-#' @examples
-#' hw <- "Hadley Wickham"
-#'
-#' str_sub(hw, 1, 6)
-#' str_sub(hw, end = 6)
-#' str_sub(hw, 8, 14)
-#' str_sub(hw, 8)
-#' str_sub(hw, c(1, 8), c(6, 14))
-#'
-#' str_sub(hw, seq_len(str_length(hw)))
-#' str_sub(hw, end = seq_len(str_length(hw)))
-str_sub <- function(string, start = 0, end = Inf) {
-  if (length(string) == 0 || length(start) == 0 || length(end) == 0) {
-    return(vector("character", 0))
-  }
-  
-  n <- max(length(string), length(start), length(end))
-  string <- rep(string, length = n)
-  start <- rep(start, length = n)
-  end <- rep(end, length = n)
-  
-  # Replace infinite ends with length of string
-  max_length <- !is.na(end) & end == Inf
-  end[max_length] <- str_length(string)[max_length]
-  
-  substring(string, start, end)
-}
-
-#' Pad a string.
-#' 
-#' @param string input character vector
-#' @param width pad strings to this minimum width
-#' @param side side on which padding character is added
-#' @param pad padding character (default is a space)
-#' @return character vector
-#' @keywords character
-#' @examples
-#' rbind(
-#'   str_pad("hadley", 30, "left"),
-#'   str_pad("hadley", 30, "right"),
-#'   str_pad("hadley", 30, "center")
-#' )
-#' # Longer strings are returned unchanged
-#' str_pad("hadley", 3)
-str_pad <- function(string, width, side = "left", pad = " ") {
-  stopifnot(length(width) == 1)
-  stopifnot(length(side) == 1)
-  stopifnot(length(pad) == 1)
-  
-  side <- match.arg(side, c("left", "right", "center"))  
-  needed <- pmax(0, width - str_length(string))
-  
-  left <- switch(side, 
-    left = needed, right = 0, center = floor(needed / 2))
-  right <- switch(side, 
-    left = 0, right = needed, center = ceiling(needed / 2))
-    
-  str_join(str_dup(pad, left), string, str_dup(pad, right))
-}
-
-#' Duplicate strings within a character vector.
-#'
-#' @param string input character vector
-#' @param times number of times to duplicate each string
-#' @return character vector
-#' @keywords internal
-str_dup <- function(string, times) {
-  # rep_matrix <- matrix(rep(string, times = times), nrow = times)
-  strings <- mlply(cbind(x = string, times), rep.int)
-  output <- unlist(llply(strings, str_join, collapse = ""))
-
-  names(output) <- names(string)
-  output
-}
\ No newline at end of file
diff --git a/R/detect.r b/R/detect.r
new file mode 100644
index 00000000..0be8db3b
--- /dev/null
+++ b/R/detect.r
@@ -0,0 +1,22 @@
+#' Detect the presence or absence of a pattern in a string.
+#'
+#' @param string input character vector
+#' @param pattern pattern to look for.  See \code{\link{regex}} for
+#'   description.
+#' @return boolean vector
+#' @seealso \code{\link{grepl}} which this function wraps
+#' @keywords character
+#' @examples
+#' fruit <- c("apple", "banana", "pear", "pinapple")
+#' str_detect(fruit, "a")
+#' str_detect(fruit, "^a")
+#' str_detect(fruit, "a$")
+#' str_detect(fruit, "b")
+#' str_detect(fruit, "[aeiou]")
+str_detect <- function(string, pattern) {
+  results <- grepl(pattern, string)
+  is.na(results) <- is.na(string)
+  
+  results
+}
+
diff --git a/R/dup.r b/R/dup.r
new file mode 100644
index 00000000..196537d3
--- /dev/null
+++ b/R/dup.r
@@ -0,0 +1,14 @@
+#' Duplicate strings within a character vector.
+#'
+#' @param string input character vector
+#' @param times number of times to duplicate each string
+#' @return character vector
+#' @keywords internal
+str_dup <- function(string, times) {
+  # rep_matrix <- matrix(rep(string, times = times), nrow = times)
+  strings <- mlply(cbind(x = string, times), rep.int)
+  output <- unlist(llply(strings, str_join, collapse = ""))
+
+  names(output) <- names(string)
+  output
+}
\ No newline at end of file
diff --git a/R/extract.r b/R/extract.r
new file mode 100644
index 00000000..1f96c5c2
--- /dev/null
+++ b/R/extract.r
@@ -0,0 +1,40 @@
+#' Extract first piece of a string that matches a pattern.
+#'
+#' @param string input character vector
+#' @param pattern pattern to look for.  See \code{\link{regex}} for
+#'   description.
+#' @return character vector.
+#' @keywords character
+#' @seealso \code{\link{str_extract_all}} to extract all matches
+#' @examples
+#' shopping_list <- c("apples x4", "flour", "sugar", "milk x2")
+#' str_extract(shopping_list, "\\d")
+#' str_extract(shopping_list, "[a-z]+")
+#' str_extract(shopping_list, "[a-z]{1,4}")
+#' str_extract(shopping_list, "\\b[a-z]{1,4}\\b")
+str_extract <- function(string, pattern) {
+  positions <- str_locate(string, pattern)
+  str_sub(string, positions[, "start"], positions[, "end"])
+}
+
+
+#' Extract all pieces of a string that match a pattern.
+#'
+#' @param string input character vector
+#' @param pattern pattern to look for.  See \code{\link{regex}} for
+#'   description.
+#' @return list of character vectors.
+#' @keywords character
+#' @seealso \code{\link{str_extract}} to extract the first match
+#' @examples
+#' shopping_list <- c("apples x4", "bag of flour", "bag of sugar", "milk x2")
+#' str_extract_all(shopping_list, "[a-z]+")
+#' str_extract_all(shopping_list, "\\b[a-z]+\\b")
+#' str_extract_all(shopping_list, "\\d")
+str_extract_all <- function(string, pattern) {
+  positions <- str_locate_all(string, pattern)
+  llply(seq_along(string), function(i) {
+    position <- positions[[i]]
+    str_sub(string[i], position[, "start"], position[, "end"])
+  })
+}
diff --git a/R/join.r b/R/join.r
new file mode 100644
index 00000000..fed2ab65
--- /dev/null
+++ b/R/join.r
@@ -0,0 +1,57 @@
+#' Join multiple strings into a single string.
+#' 
+#' @param ... one or more character vectors.  Zero length arguments 
+#'   are removed
+#' @param sep string to insert between input vectors
+#' @param collapse optional string used to combine input vectors into single
+#'   string
+#' @return If \code{collapse = NULL} (the default) a character vector with 
+#'   length equal to the longest input string.  If \code{collapse} is non-
+#'   NULL, a character vector of length 1.
+#' @keywords character
+#' @seealso \code{\link{paste}} which this function wraps
+#' @examples
+#' str_join("Letter: ", letters)
+#' str_join("Letter", letters, sep = ": ")
+#' str_join(letters, " is for", "...")
+#' str_join(letters[-26], " comes before ", letters[-1])
+#'
+#' str_join(letters, collapse = "")
+#' str_join(letters, collapse = ", ")
+str_join <- function(..., sep = "", collapse = NULL) {
+  strings <- Filter(function(x) length(x) > 0, list(...))
+  
+  do.call("paste", c(strings, list(sep = sep, collapse = collapse)))
+}
+
+#' Pad a string.
+#' 
+#' @param string input character vector
+#' @param width pad strings to this minimum width
+#' @param side side on which padding character is added
+#' @param pad padding character (default is a space)
+#' @return character vector
+#' @keywords character
+#' @examples
+#' rbind(
+#'   str_pad("hadley", 30, "left"),
+#'   str_pad("hadley", 30, "right"),
+#'   str_pad("hadley", 30, "center")
+#' )
+#' # Longer strings are returned unchanged
+#' str_pad("hadley", 3)
+str_pad <- function(string, width, side = "left", pad = " ") {
+  stopifnot(length(width) == 1)
+  stopifnot(length(side) == 1)
+  stopifnot(length(pad) == 1)
+  
+  side <- match.arg(side, c("left", "right", "center"))  
+  needed <- pmax(0, width - str_length(string))
+  
+  left <- switch(side, 
+    left = needed, right = 0, center = floor(needed / 2))
+  right <- switch(side, 
+    left = 0, right = needed, center = ceiling(needed / 2))
+    
+  str_join(str_dup(pad, left), string, str_dup(pad, right))
+}
\ No newline at end of file
diff --git a/R/length.r b/R/length.r
new file mode 100644
index 00000000..24903f2b
--- /dev/null
+++ b/R/length.r
@@ -0,0 +1,16 @@
+#' The length of a string (in characters).
+#'
+#' @param string input character vector
+#' @return numeric vector giving number of characters in each element of the 
+#'   character vector.  Missing string have missing length.
+#' @keywords character
+#' @seealso \code{\link{nchar}} which this function wraps
+#' @examples
+#' str_length(letters)
+#' str_length(c("i", "like", "programming", NA))
+str_length <- function(string) {
+  string <- as.character(string)
+  nc <- nchar(string)
+  is.na(nc) <- is.na(string)
+  nc
+}
\ No newline at end of file
diff --git a/R/locate.r b/R/locate.r
new file mode 100644
index 00000000..0f806b5f
--- /dev/null
+++ b/R/locate.r
@@ -0,0 +1,66 @@
+#' Locate the position of the first occurence of a pattern in a string.
+#'
+#' @param string input character vector
+#' @param pattern pattern to look for.  See \code{\link{regex}} for
+#'   description.
+#' @return numeric matrix.  First column gives start postion of match, and
+#'   second column gives end position.
+#' @keywords character
+#' @seealso 
+#'   \code{\link{regexpr}} which this function wraps
+#' 
+#'   \code{\link{str_extract}} for a convenient way of extracting matches
+#  
+#'   \code{\link{str_locate_all}} to locate position of all matches
+#'
+#' @examples
+#' fruit <- c("apple", "banana", "pear", "pinapple")
+#' str_locate(fruit, "a")
+#' str_locate(fruit, "e")
+str_locate <- function(string, pattern) {
+  match <- regexpr(pattern, string)  
+  
+  start <- as.vector(match)
+  end <- start + attr(match, "match.length") - 1
+  
+  missing <- start == -1
+  start[missing] <- NA
+  end[missing] <- NA
+  
+  cbind(start = start, end = end)
+}
+
+#' Locate the position of all occurences of a pattern in a string.
+#'
+#' @param string input character vector
+#' @param pattern pattern to look for.  See \code{\link{regex}} for
+#'   description.
+#' @keywords character
+#' @return list of numeric matrices.  First column gives start postion of
+#'   match, and second column gives end position.
+#' @seealso
+#'  \code{\link{regexpr}} which this function wraps
+#'
+#'  \code{\link{str_extract}} for a convenient way of extracting matches
+#'
+#'  \code{\link{str_locate}} to locate position of first match
+#' 
+#' @examples
+#' fruit <- c("apple", "banana", "pear", "pinapple")
+#' str_locate_all(fruit, "a")
+#' str_locate_all(fruit, "e")
+str_locate_all <- function(string, pattern) {
+  matches <- gregexpr(pattern, string)  
+  
+  null <- matrix(0, nrow = 0, ncol = 2)
+  colnames(null) <- c("start", "end")
+  
+  llply(matches, function(match) {
+    if (length(match) == 1 && match == -1) return(null)
+    
+    start <- as.vector(match)
+    end <- start + attr(match, "match.length") - 1
+    cbind(start = start, end = end)
+  })
+}
+
diff --git a/R/regexp.r b/R/regexp.r
deleted file mode 100644
index 142a6eba..00000000
--- a/R/regexp.r
+++ /dev/null
@@ -1,172 +0,0 @@
-#' Detect the presence or absence of a pattern in a string.
-#'
-#' @param string input character vector
-#' @param pattern pattern to look for.  See \code{\link{regex}} for
-#'   description.
-#' @return boolean vector
-#' @seealso \code{\link{grepl}} which this function wraps
-#' @keywords character
-#' @examples
-#' fruit <- c("apple", "banana", "pear", "pinapple")
-#' str_detect(fruit, "a")
-#' str_detect(fruit, "^a")
-#' str_detect(fruit, "a$")
-#' str_detect(fruit, "b")
-#' str_detect(fruit, "[aeiou]")
-str_detect <- function(string, pattern) {
-  results <- grepl(pattern, string)
-  is.na(results) <- is.na(string)
-  
-  results
-}
-
-#' Locate the position of the first occurence of a pattern in a string.
-#'
-#' @param string input character vector
-#' @param pattern pattern to look for.  See \code{\link{regex}} for
-#'   description.
-#' @return numeric matrix.  First column gives start postion of match, and
-#'   second column gives end position.
-#' @keywords character
-#' @seealso 
-#'   \code{\link{regexpr}} which this function wraps
-#' 
-#'   \code{\link{str_extract}} for a convenient way of extracting matches
-#  
-#'   \code{\link{str_locate_all}} to locate position of all matches
-#'
-#' @examples
-#' fruit <- c("apple", "banana", "pear", "pinapple")
-#' str_locate(fruit, "a")
-#' str_locate(fruit, "e")
-str_locate <- function(string, pattern) {
-  match <- regexpr(pattern, string)  
-  
-  start <- as.vector(match)
-  end <- start + attr(match, "match.length") - 1
-  
-  missing <- start == -1
-  start[missing] <- NA
-  end[missing] <- NA
-  
-  cbind(start = start, end = end)
-}
-
-#' Locate the position of all occurences of a pattern in a string.
-#'
-#' @param string input character vector
-#' @param pattern pattern to look for.  See \code{\link{regex}} for
-#'   description.
-#' @keywords character
-#' @return list of numeric matrices.  First column gives start postion of
-#'   match, and second column gives end position.
-#' @seealso
-#'  \code{\link{regexpr}} which this function wraps
-#'
-#'  \code{\link{str_extract}} for a convenient way of extracting matches
-#'
-#'  \code{\link{str_locate}} to locate position of first match
-#' 
-#' @examples
-#' fruit <- c("apple", "banana", "pear", "pinapple")
-#' str_locate_all(fruit, "a")
-#' str_locate_all(fruit, "e")
-str_locate_all <- function(string, pattern) {
-  matches <- gregexpr(pattern, string)  
-  
-  null <- matrix(0, nrow = 0, ncol = 2)
-  colnames(null) <- c("start", "end")
-  
-  llply(matches, function(match) {
-    if (length(match) == 1 && match == -1) return(null)
-    
-    start <- as.vector(match)
-    end <- start + attr(match, "match.length") - 1
-    cbind(start = start, end = end)
-  })
-}
-
-#' Extract first piece of a string that matches a pattern.
-#'
-#' @param string input character vector
-#' @param pattern pattern to look for.  See \code{\link{regex}} for
-#'   description.
-#' @return character vector.
-#' @keywords character
-#' @seealso \code{\link{str_extract_all}} to extract all matches
-#' @examples
-#' shopping_list <- c("apples x4", "flour", "sugar", "milk x2")
-#' str_extract(shopping_list, "\\d")
-#' str_extract(shopping_list, "[a-z]+")
-#' str_extract(shopping_list, "[a-z]{1,4}")
-#' str_extract(shopping_list, "\\b[a-z]{1,4}\\b")
-str_extract <- function(string, pattern) {
-  positions <- str_locate(string, pattern)
-  str_sub(string, positions[, "start"], positions[, "end"])
-}
-
-
-#' Extract all pieces of a string that match a pattern.
-#'
-#' @param string input character vector
-#' @param pattern pattern to look for.  See \code{\link{regex}} for
-#'   description.
-#' @return list of character vectors.
-#' @keywords character
-#' @seealso \code{\link{str_extract}} to extract the first match
-#' @examples
-#' shopping_list <- c("apples x4", "bag of flour", "bag of sugar", "milk x2")
-#' str_extract_all(shopping_list, "[a-z]+")
-#' str_extract_all(shopping_list, "\\b[a-z]+\\b")
-#' str_extract_all(shopping_list, "\\d")
-str_extract_all <- function(string, pattern) {
-  positions <- str_locate_all(string, pattern)
-  llply(seq_along(string), function(i) {
-    position <- positions[[i]]
-    str_sub(string[i], position[, "start"], position[, "end"])
-  })
-}
-
-#' Replace replaced occurences of a matched pattern in a string.
-#'
-#' @param string input character vector
-#' @param pattern pattern to look for.  See \code{\link{regex}} for
-#'   description.
-#' @param replacement replacement string.  References of the form \code{\1}, 
-#'   \code{\2} will be replaced with the contents of the respective matched
-#'   group (created by \code{()}) within the pattern.
-#' @return character vector.
-#' @keywords character
-#' @seealso \code{\link{gsub}} which this function wraps
-str_replace <- function(string, pattern, replacement) {
-  gsub(pattern, replacement, string)
-}
-
-
-#' Split up a string by a pattern.
-#' 
-#' @param string input character vector
-#' @param pattern pattern to split up string by.  See \code{\link{regex}} for
-#'   description.  If \code{NA}, returns original string.  If \code{""} splits
-#'   into individual characters.
-#' @param n maximum number of pieces to return.  Default (Inf) uses all
-#'   possible split positions 
-#' @return a list of character vectors.
-#' @keywords character
-#' @seealso \code{\link{strsplit}} which this function wraps
-str_split <- function(string, pattern, n = Inf) {
-  string <- as.character(string)
-  if (n == Inf) {
-    strsplit(string, pattern)    
-  } else if (n == 1) {
-    string
-  } else {
-    locations <- str_locate_all(string, pattern)
-    llply(locations, function(mat) {      
-      cut <- mat[seq_len(min(n - 1, nrow(mat))), , drop = FALSE]
-      keep <- matrix(c(0, t(cut), Inf), ncol = 2, byrow = TRUE)
-      
-      str_sub(string, keep[, 1] + 1, keep[, 2] - 1)
-    })
-  } 
-}
diff --git a/R/replace.r b/R/replace.r
new file mode 100644
index 00000000..2fa6e1ba
--- /dev/null
+++ b/R/replace.r
@@ -0,0 +1,28 @@
+
+#' Replace replaced occurences of a matched pattern in a string.
+#'
+#' @param string input character vector
+#' @param pattern pattern to look for.  See \code{\link{regex}} for
+#'   description.
+#' @param replacement replacement string.  References of the form \code{\1}, 
+#'   \code{\2} will be replaced with the contents of the respective matched
+#'   group (created by \code{()}) within the pattern.
+#' @return character vector.
+#' @keywords character
+#' @seealso \code{\link{gsub}} which this function wraps
+str_replace <- function(string, pattern, replacement) {
+  gsub(pattern, replacement, string)
+}
+
+
+#' Trim whitespace from start and end of string.
+#' 
+#' @param string input character vector
+#' @return character vector with leading and trailing whitespace removed
+#' @keywords character
+#' @examples
+#' str_trim("  String with trailing and leading white space\t")
+#' str_trim("\n\nString with trailing and leading white space\n\n")
+str_trim <- function(string) {
+  str_replace(string, "^\\s+|\\s+$", "")
+}
diff --git a/R/split.r b/R/split.r
new file mode 100644
index 00000000..b7227e38
--- /dev/null
+++ b/R/split.r
@@ -0,0 +1,28 @@
+
+#' Split up a string by a pattern.
+#' 
+#' @param string input character vector
+#' @param pattern pattern to split up string by.  See \code{\link{regex}} for
+#'   description.  If \code{NA}, returns original string.  If \code{""} splits
+#'   into individual characters.
+#' @param n maximum number of pieces to return.  Default (Inf) uses all
+#'   possible split positions 
+#' @return a list of character vectors.
+#' @keywords character
+#' @seealso \code{\link{strsplit}} which this function wraps
+str_split <- function(string, pattern, n = Inf) {
+  string <- as.character(string)
+  if (n == Inf) {
+    strsplit(string, pattern)    
+  } else if (n == 1) {
+    string
+  } else {
+    locations <- str_locate_all(string, pattern)
+    llply(locations, function(mat) {      
+      cut <- mat[seq_len(min(n - 1, nrow(mat))), , drop = FALSE]
+      keep <- matrix(c(0, t(cut), Inf), ncol = 2, byrow = TRUE)
+      
+      str_sub(string, keep[, 1] + 1, keep[, 2] - 1)
+    })
+  } 
+}
diff --git a/R/sub.r b/R/sub.r
new file mode 100644
index 00000000..09d5cee6
--- /dev/null
+++ b/R/sub.r
@@ -0,0 +1,42 @@
+#' Extract substrings from a character vector.
+#'
+#' \code{sub_str} will replicate all arguments to be the same length as the 
+#' longest argument.  If any arguments are of length 0, the output will be 
+#' a zero length character vector.
+#'
+#' @param string input character vector
+#' @param start integer vector giving position of first charater in substring, 
+#'   defaults to first character.
+#' @param end integer vector giving position of last character in substring, 
+#'   defaults to last character.
+#' @return character vector of substring.  Will be length of longest input
+#'   argument
+#' @keywords character
+#' @seealso \code{\link{substring}} which this function wraps
+#' @examples
+#' hw <- "Hadley Wickham"
+#'
+#' str_sub(hw, 1, 6)
+#' str_sub(hw, end = 6)
+#' str_sub(hw, 8, 14)
+#' str_sub(hw, 8)
+#' str_sub(hw, c(1, 8), c(6, 14))
+#'
+#' str_sub(hw, seq_len(str_length(hw)))
+#' str_sub(hw, end = seq_len(str_length(hw)))
+str_sub <- function(string, start = 0, end = Inf) {
+  if (length(string) == 0 || length(start) == 0 || length(end) == 0) {
+    return(vector("character", 0))
+  }
+  
+  n <- max(length(string), length(start), length(end))
+  string <- rep(string, length = n)
+  start <- rep(start, length = n)
+  end <- rep(end, length = n)
+  
+  # Replace infinite ends with length of string
+  max_length <- !is.na(end) & end == Inf
+  end[max_length] <- str_length(string)[max_length]
+  
+  substring(string, start, end)
+}
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