(* StringCvt -- SML Basis Library *) datatype radix = BIN | OCT | DEC | HEX datatype realfmt =     SCI of int option   (* scientific,  arg = # dec. digits, dflt=6 *)  | FIX of int option   (* fixed-point, arg = # dec. digits, dflt=6 *)  | GEN of int option   (* auto choice of the above,                *)                        (* arg = # significant digits, dflt=12      *) type cs                 (* character source state *) type ('a, 'b) reader = 'b -> ('a * 'b) option val scanString : ((char, cs) reader -> ('a, cs) reader) -> string -> 'a option val splitl     : (char -> bool) -> (char, 'a) reader -> 'a -> string * 'aval takel      : (char -> bool) -> (char, 'a) reader -> 'a -> string val dropl      : (char -> bool) -> (char, 'a) reader -> 'a -> 'a val skipWS     : (char, 'a) reader -> 'a -> 'a  val padLeft    : char -> int -> string -> stringval padRight   : char -> int -> string -> string (*    This structure presents tools for scanning strings and values from   functional character streams, and for simple formatting.    [('elm, 'src) reader] is the type of source readers for reading a   sequence of 'elm values from a source of type 'src.  For instance,    a character source reader        getc : (char, cs) reader    is used for obtaining characters from a functional character source   src of type cs, one at a time. It should hold that         getc src = SOME(c, src')        if the next character in src                                         is c, and src' is the rest of src;                 = NONE                 if src contains no characters    A character source scanner takes a character source reader getc as   argument and uses it to scan a data value from the character   source.    [scanString scan s] turns the string s into a character source and   applies the scanner `scan' to that source.    [splitl p getc src] returns (pref, suff) where pref is the   longest prefix (left substring) of src all of whose characters   satisfy p, and suff is the remainder of src.  That is, the first   character retrievable from suff, if any, is the leftmost character   not satisfying p.  Does not skip leading whitespace.    [takel p getc src] returns the longest prefix (left substring) of   src all of whose characters satisfy predicate p.  That is, if the   left-most character does not satisfy p, the result is the empty   string.  Does not skip leading whitespace.  It holds that        takel p getc src = #1 (splitl p getc src)    [dropl p getc src] drops the longest prefix (left substring) of   src all of whose characters satisfy predicate p.  If all characters   do, it returns the empty source.  It holds that        dropl p getc src = #2 (splitl p getc src)    [skipWS getc src] drops any leading whitespace from src.   Equivalent to dropl Char.isSpace.    [padLeft c n s] returns the string s if size s >= n, otherwise pads   s with (n - size s) copies of the character c on the left.     In other words, right-justifies s in a field n characters wide.    [padRight c n s] returns the string s if size s >= n, otherwise pads   s with (n - size s) copies of the character c on the right.   In other words, left-justifies s in a field n characters wide.*)