= string: append, drop, in, prefix, quoted, splitl, splitr, splitstrl, splitstrr, take, tobig, toint, toreal, tolower, toupper, unquoted: string operations     include "string.m";    str := load String String->PATH;     append:    fn(s: string, l: list of string): list of string;    drop:      fn(s, cl: string): string;    in:        fn(c: int, cl: string): int;    prefix:    fn(pre, s: string): int;    splitl:    fn(s, cl: string): (string, string);    splitr:    fn(s, cl: string): (string, string);    splitstrl: fn(s, t: string): (string, string);    splitstrr: fn(s, t: string): (string, string);    take:      fn(s, cl: string): string;    tobig:     fn(s: string, base: int): (big, string);    toint:     fn(s: string, base: int): (int, string);    toreal:    fn(s: string, base: int): (real, string);    tolower:   fn(s: string): string;    toupper:   fn(s: string): string;    quoted:    fn(args: list of string): string;    unquoted:  fn(s: string): list of string; The  cl  argument  to  some of these functions is a character= class in which a: between any  two  characters  indicates  arange  and  a ^ in the first position means not in the class.Example of classes are "a-zA-Z" and "^acg-mr". Append appends string s to the end of string list l. Drop removes the maximal prefix of string s that is in  classcl. In  returns  1  if  character c is in class cl and 0 if it isnot. Prefix returns 1 if string pre is a prefix of string s and  0if it is not. Splitl  splits  string  s  just before the first character inclass cl. Splitr splits string s just after the last character in classcl. Splitstrl splits string s just before the leftmost segment ofstring s that consists entirely of string t,  and  returns  atuple  with  the  resulting  pair  of strings.  If t does notoccur in s, the result is (s,nil). Splitstrr splits string s just after the rightmost segment ofstring  s  that  consists entirely of string t, and returns atuple with the resulting pair of  strings.   If  t  does  notoccur in s, the result is (nil,s). Take  returns the maximal prefix of string s that is in classcl. Toint returns as an integer  the  value  represented  by  thestring  s.   The  string is scanned up to the first characterinconsistent with base.   The  first  inconsistent  charactermarks  the  beginning of the returned string.  Leading white-space characters are ignored.  The base can be any integer inthe range 2 to 36, inclusive; or 0 in which case the base canbe specified as part of the  string,  in  Limbo  style  (e.g.16rffff). Tobig  has  the  same specification as toint except that con‐verts to 64-bit big. Toreal is similar to toint, except that it expects  a  float‐ing-point  number  after  optional  leading  white  space: anoptional sign, then a string of digits containing  a  decimalpoint,  then an optional `e' or `E' followed by an optionallysigned decimal integer exponent.  The string  of  digits  canoptionally  be  preceded  by  a base (radix) specifier of theform Br, as for integers.  Any exponent is  then  interpretedas  a power of that base.  Alternatively, following any lead‐ing white space and an optional sign, either nan or  infinitycan appear, in any case, and toreal will return the appropri‐ate value for IEEE floating-point. Tolower converts all upper case letters in the  string  s  tolower case letters. Toupper  converts  all  lower case letters in the string s toupper case letters. Quoted takes a list of strings, args, and  returns  a  singlestring  with the value of each element of args separated fromthe next by a single space.  When  forming  the  string,  thetext  of  any  element  that  contains  white space or singlequotes is first quoted by surrounding  it  by  single  quotes('...')   within  which each existing single quote is doubled(''), following the conventions of sh(1). Unquoted takes a string s, quoted according  to  the  conven‐tions  of  quoted,  and  splits it into separate strings.  Itsplits the string at each maximal sequence of unquoted  whitespace (blank, newline or tab), stripping single quotes exceptwhere paired, to form  the  corresponding  list  of  strings,which it returns. == source/appl/lib/string.b