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NAME

       io_lib - IO Library Functions

DESCRIPTION

       This  module  contains functions for converting to and from strings (lists of characters).
       They are used for implementing the functions in the io module. There is no guarantee  that
       the  character lists returned from some of the functions are flat, they can be deep lists.
       lists:flatten/1 can be used for flattening deep lists.

DATA TYPES

       chars() = [char() | chars()]

       continuation()

              A continuation as returned by fread/3.

       depth() = -1 | integer() >= 0

       fread_error() = atom
                     | based
                     | character
                     | float
                     | format
                     | input
                     | integer
                     | string
                     | unsigned

       fread_item() = string() | atom() | integer() | float()

       latin1_string() = [unicode:latin1_char()]

EXPORTS

       nl() -> string()

              Returns a character list which represents a new line character.

       write(Term) -> chars()

       write(Term, Depth) -> chars()

              Types:

                 Term = term()
                 Depth = depth()

              Returns a character list which represents Term. The Depth  (-1)  argument  controls
              the  depth  of  the  structures  written.  When  the  specified  depth  is reached,
              everything below this level is replaced by "...". For example:

              1> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9})).
              "{1,[2],[3],[4,5],6,7,8,9}"
              2> lists:flatten(io_lib:write({1,[2],[3],[4,5],6,7,8,9}, 5)).
              "{1,[2],[3],[...],...}"

       print(Term) -> chars()

       print(Term, Column, LineLength, Depth) -> chars()

              Types:

                 Term = term()
                 Column = LineLength = integer() >= 0
                 Depth = depth()

              Also returns a list of characters which represents Term, but breaks representations
              which  are  longer than one line into many lines and indents each line sensibly. It
              also tries to detect and output lists of printable characters as strings. Column is
              the  starting  column  (1), LineLength the maximum line length (80), and Depth (-1)
              the maximum print depth.

       fwrite(Format, Data) -> chars()

       format(Format, Data) -> chars()

              Types:

                 Format = io:format()
                 Data = [term()]

              Returns a character list which represents Data formatted in accordance with Format.
              See io:fwrite/1,2,3 for a detailed description of the available formatting options.
              A fault is generated if there is an error in the format string or argument list.

              If (and only if) the Unicode translation modifier is  used  in  the  format  string
              (i.e. ~ts or ~tc), the resulting list may contain characters beyond the ISO-latin-1
              character range (in other words, numbers larger than 255). If so, the result is not
              an ordinary Erlang string(), but can well be used in any context where Unicode data
              is allowed.

       fread(Format, String) -> Result

              Types:

                 Format = String = string()
                 Result = {ok,
                           InputList :: [fread_item()],
                           LeftOverChars :: string()}
                        | {more,
                           RestFormat :: string(),
                           Nchars :: integer() >= 0,
                           InputStack :: chars()}
                        | {error, {fread, What :: fread_error()}}

              Tries to read String in accordance  with  the  control  sequences  in  Format.  See
              io:fread/3  for  a  detailed description of the available formatting options. It is
              assumed that String contains whole lines. It returns:

                {ok, InputList, LeftOverChars}:
                  The string was read. InputList is the list of  successfully  matched  and  read
                  items, and LeftOverChars are the input characters not used.

                {more, RestFormat, Nchars, InputStack}:
                  The string was read, but more input is needed in order to complete the original
                  format string. RestFormat is the remaining format string, Nchars the number  of
                  characters scanned, and InputStack is the reversed list of inputs matched up to
                  that point.

                {error, What}:
                  The read operation failed and the parameter What gives a hint about the error.

              Example:

              3> io_lib:fread("~f~f~f", "15.6 17.3e-6 24.5").
              {ok,[15.6,1.73e-5,24.5],[]}

       fread(Continuation, CharSpec, Format) -> Return

              Types:

                 Continuation = continuation() | []
                 CharSpec = string() | eof
                 Format = string()
                 Return = {more, Continuation1 :: continuation()}
                        | {done, Result, LeftOverChars :: string()}
                 Result = {ok, InputList :: [fread_item()]}
                        | eof
                        | {error, {fread, What :: fread_error()}}

              This is the re-entrant formatted reader. The continuation of the first call to  the
              functions   must   be  [].  Refer  to  Armstrong,  Virding,  Williams,  'Concurrent
              Programming in Erlang', Chapter 13 for a complete description of how the re-entrant
              input scheme works.

              The function returns:

                {done, Result, LeftOverChars}:
                  The input is complete. The result is one of the following:

                  {ok, InputList}:
                    The  string  was read. InputList is the list of successfully matched and read
                    items, and LeftOverChars are the remaining characters.

                  eof:
                    End of file has been encountered. LeftOverChars are the input characters  not
                    used.

                  {error, What}:
                    An error occurred and the parameter What gives a hint about the error.

                {more, Continuation}:
                  More  data is required to build a term. Continuation must be passed to fread/3,
                  when more data becomes available.

       write_atom(Atom) -> chars()

              Types:

                 Atom = atom()

              Returns the list of characters needed to print the atom Atom.

       write_string(String) -> chars()

              Types:

                 String = string()

              Returns the list of characters needed to print String as a string.

       write_string_as_latin1(String) -> latin1_string()

              Types:

                 String = string()

              Returns the list of characters needed to print  String  as  a  string.  Non-Latin-1
              characters are escaped.

       write_latin1_string(Latin1String) -> latin1_string()

              Types:

                 Latin1String = latin1_string()

              Returns the list of characters needed to print Latin1String as a string.

       write_char(Char) -> chars()

              Types:

                 Char = char()

              Returns  the list of characters needed to print a character constant in the Unicode
              character set.

       write_char_as_latin1(Char) -> latin1_string()

              Types:

                 Char = char()

              Returns the list of characters needed to print a character constant in the  Unicode
              character set. Non-Latin-1 characters are escaped.

       write_latin1_char(Latin1Char) -> latin1_string()

              Types:

                 Latin1Char = unicode:latin1_char()

              Returns  the  list  of  characters needed to print a character constant in the ISO-
              latin-1 character set.

       indentation(String, StartIndent) -> integer()

              Types:

                 String = string()
                 StartIndent = integer()

              Returns the indentation if String has been printed, starting at StartIndent.

       char_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns true if Term is a flat list of characters in the Unicode  range,  otherwise
              it returns false.

       latin1_char_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns  true  if  Term  is  a  flat  list  of characters in the ISO-latin-1 range,
              otherwise it returns false.

       deep_char_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns true if Term is a, possibly deep, list of characters in the Unicode  range,
              otherwise it returns false.

       deep_latin1_char_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns  true  if  Term  is a, possibly deep, list of characters in the ISO-latin-1
              range, otherwise it returns false.

       printable_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns true if Term is a flat list of printable characters, otherwise  it  returns
              false.

              What  is  a printable character in this case is determined by the +pc start up flag
              to the Erlang VM. See io:printable_range/0 and erl(1).

       printable_latin1_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns true if Term is a flat list of printable ISO-latin-1 characters,  otherwise
              it returns false.

       printable_unicode_list(Term) -> boolean()

              Types:

                 Term = term()

              Returns  true  if Term is a flat list of printable Unicode characters, otherwise it
              returns false.