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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 following description, many functions have an optional parameter IoDe- vice. 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 generate aesthetically attrac- tive representations of abstract forms, which are suitable for print- ing. 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 compiler 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 consumed 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 returning 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 returning 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 detects 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 applica- tion 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)
NAME | SYNOPSIS | DATA TYPES | EXPORTS | ERROR INFORMATION | AUTHORS
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