RosettaCodeData/Task/S-Expressions/00DESCRIPTION

[[wp:S-Expression|S-Expressions]]   are one convenient way to parse and store data.


;Task:
Write a simple reader and writer for S-Expressions that handles quoted and unquoted strings, integers and floats.

The reader should read a single but nested S-Expression from a string and store it in a suitable datastructure (list, array, etc).

Newlines and other whitespace may be ignored unless contained within a quoted string.

“<tt>()</tt>” &nbsp; inside quoted strings are not interpreted, but treated as part of the string.

Handling escaped quotes inside a string is optional; &nbsp; thus “<tt>(foo"bar)</tt>” maybe treated as a string “<tt>foo"bar</tt>”, or as an error.

For this, the reader need not recognize “<tt>\</tt>” for escaping, but should, in addition, recognize numbers if the language has appropriate datatypes.

Languages that support it may treat unquoted strings as symbols.

Note that with the exception of “<tt>()"</tt>” (“<tt>\</tt>” if escaping is supported) and whitespace there are no special characters. Anything else is allowed without quotes.

The reader should be able to read the following input
<lang lisp>((data "quoted data" 123 4.5)
 (data (!@# (4.5) "(more" "data)")))</lang>
and turn it into a native datastructure. (see the [[#Pike|Pike]], [[#Python|Python]] and [[#Ruby|Ruby]] implementations for examples of native data structures.)

The writer should be able to take the produced list and turn it into a new S-Expression.
Strings that don't contain whitespace or parentheses () don't need to be quoted in the resulting S-Expression, but as a simplification, any string may be quoted.


;Extra Credit:
Let the writer produce pretty printed output with indenting and line-breaks.
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