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lfe_io(3)		    Library Functions Manual		       lfe_io(3)

NAME
     lfe_io - Lisp Flavoured Erlang (LFE) io functions

SYNOPSIS
     This  module  provides a standard set of io functions for LFE.  In the fol-
     lowing description, many functions have an optional parameter IoDevice.  If
     included, it must be the pid of a process which handles  the  IO  protocols
     such as the IoDevice returned by file:open/2.

     Two functions in this module are used to generateA aesthetically attractive
     representations  of abstract forms, which are suitable for printing.  These
     functions return (possibly deep) lists of characters and generate an  error
     if the form is wrong.

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

     prompt() = atom() | unicode:chardata()

     filesexpr() = {Sexpr,Line}

     This  is the format returned by lfe_io:parse_file/1 and is used by the com-
     piler to give better error information.

EXPORTS
     get_line() -> Data | {error, ErrorInfo} | eof

     get_line(Prompt) -> Data | {error, ErrorInfo} | eof

     get_line(IoDevice, Prompt) -> Data | {error, ErrorInfo} | eof

     Reads a line from the standard input (IoDevice), prompting it  with  prompt
     (Prompt).	 Note  that  this call guarantees that the input is saved in the
     input history.

     read() -> {ok, Sexpr} | {error, ErrorInfo} | eof

     read(Prompt) -> {ok, Sexpr} | {error, ErrorInfo} | eof

     read(IoDevice, Prompt) -> {ok, Sexpr} | {error, ErrorInfo} | eof

     Read an s-expr from the standard input (IoDevice) with a  prompt  (Prompt).
     Note that this is not line-oriented in that it stops as soon as it has con-
     sumed enough characters.

     read_line() -> {ok, Sexpr} | {error, ErrorInfo} | eof

     read_line(Prompt) -> {ok, Sexpr} | {error, ErrorInfo} | eof

     read_line(IoDevice, Prompt) -> {ok, Sexpr} | {error, ErrorInfo} | eof

     Read  the	first  s-expr  from  the standard input (IoDevice) with a prompt
     (Prompt).	Note that this is line-oriented in that  it  reads  whole  lines
     discarding left-over characters in the last line.

     read_string(String) -> {ok, [Sexpr]} | {error, ErrorInfo}

     Read all the s-exprs from String.

     print(Sexpr) -> ok

     print(IoDevice, Sexpr) -> ok

     Print the s-expr Sexpr to the standard output (IoDevice).

     print1(Sexpr) -> DeepCharList

     Return the list of characters which represent the s-expr Sexpr.

     prettyprint(Sexpr) -> ok

     prettyprint(IoDevice, Sexpr) -> ok

     Pretty print the s-expr Sexpr to the standard output (IoDevice).

     prettyprint1(Sexpr) -> DeepCharList

     prettyprint1(Sexpr, Depth) -> DeepCharList

     prettyprint1(Sexpr, Depth, Indentation) -> DeepCharList

     prettyprint1(Sexpr, Depth, Indentation, LineLength) -> DeepCharList

     Return  the  list	of  characters which represents the prettyprinted s-expr
     Sexpr.  Default values for Depth is 30, Indentation is 0 and LineLength  is
     80.

     format(Format, Args) -> ok

     format(IoDevice, Format, Args) -> ok

     fwrite(Format, Args) -> ok

     fwrite(IoDevice, Format, Args) -> ok

     Print  formatted  output.	 The  following commands are valid in the format
     string:

     * ~w, ~W	  - print LFE terms

     * ~p, ~P	  - prettyprint LFE terms

     * ~s	  - print a string

     * ~e, ~f, ~g - print floats

     * ~b, ~B	  - based integers

     * ~x, ~X	  - based integers with a prefix

     * ~+, ~#	  - based integers in vanilla erlang format

     * ~~	  - prints ~

     * ~c, ~n, ~i

     Currently they behave as for vanilla erlang except  that  ~w,  ~W,  ~p,  ~P
     print the terms as LFE sexprs.

     format1(Format, Args) -> DeepCharList

     fwrite1(Format, Args) -> DeepCharList

     Return the formatted output with same arguments as format/fwrite.

     read_file(FileName|Fd) -> {ok,[Sexpr]} | {error,ErrorInfo}

     read_file(FileName|Fd, Line) -> {ok, [Sexpr]} | {error, ErrorInfo}

     Read  the file Filename or the already opened file's file descriptor Fd re-
     turning a list of s-exprs.

     parse_file(FileName|Fd) -> {ok, [FileSexpr]} | {error, ErrorInfo}

     parse_file(FileName|Fd, Line) -> {ok, [FileSexpr]} | {error, ErrorInfo}

     where

     FileSexpr = filesexpr()

     Read the file Filename or the already opened file's file descriptor Fd  re-
     turning  a  list of pairs containing s-expr and line number of the start of
     the s-expr.

     scan_sexpr(Cont, Chars) -> {done, Ret, RestChars} | {more, Cont1}

     scan_sexpr(Cont, Chars, Line) -> {done, Ret, RestChars} | {more, Cont1}

     This is a re-entrant call which scans tokens from the input and  returns  a
     parsed  sepxr.   If  there are enough characters to parse a sexpr or it de-
     tects and error then it returns {done,...} otherwise it returns {more,Cont}
     where Cont is used in the next call to scan_sexpr with more  characters  to
     try  and  parse  a sexpr.	This is continued until a sexpr has been parsed.
     Cont is initially [].

     It is not designed to be called directly by an application but used through
     the i/o system where it can typically be called in an application by:

     io:request(In, {get_until,unicode,Prompt,Module,scan_sexpr,[Line]})

ERROR INFORMATION
     The ErrorInfo mentioned above is the standard ErrorInfo structure which  is
     returned from all IO modules.  It has the following format:

     {ErrorLine, Module, ErrorDescriptor}

     A string describing the error is obtained with the following call:

	    apply(Module, format_error, ErrorDescriptor)

AUTHORS
     Robert Virding.

				    2008-2024			       lfe_io(3)

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