This library is intended as simple replacement for XML parsing libraries for those, that prefer lisp sexp syntax over XML.

To use it you only have to include these 2 files in your project: lispparser.h and lispparser.cpp, and to add #include "lispparser.h" in your code.
Code only depends on STL, so no external libraries are needed.

Example of usage is in main.cpp.

Library is contained in one namespace AjucLispParser. The one function that is intended for end-user is

const Expression* parse(istringstream& input);

This function tries to read from input stream input the first form and parse it to Expression.

Expression is abstract base class - its sub-classes are Float, String, Atom, Identifier and List. List is a Expression that can contain other Expressions - it can be arbitrarily deep nested.

Examples of inputs and resulting Expression trees:

1                     Float   - value == 1.0f
1.0                   Float   - value == 1.0f
"lorem ipsum"         String  - value == "lorem ipsum"
:some-name            Atom    - name is :some-name
some-name             Identifier - name is some-name
()                    List - empty list
(1 2 "lorem-ipsum")   List - has 3 elements - first and second are Floats, the last is String
( () (1 2) ((1)))     List containing: Empty list, List with 2 Floats, and List with one list inside, containing Float.

Every Expression subclass has method toString() which returns string representation of given expression, that can be read back by parse function.

Spaces, Tabs, Line breaks (Enters) and commas (,) are considered whitespace, so (1 2 3) is equivalent to (1 2,,,, 3,,).

There are 3 types of parentheses: (), [], {}. They can be used interchangeably, but if kinds of parentheses doesn't match, parse will report error.

So these forms are equivalent:
[ [1 2 3] [4 5 6] ]
{ (1 2 3) [4 5 6] }
( (1 2 3) {4 5 6} )
( (1 2 3) (4 5 6) )
etc.

But this won't parse:
( [1 2 3) {4 5 6} ]


Parse returns shared_ptr to Expression, possibly containing other expressions, each through shared_ptr. There can be no cycles inside (this arises naturally from the way parser works).

If input stream contains More than one top-level form, the first invocation of parse will return the first form, and the second invocation of parse on the same stream will return second form, and so on.

Hope it will be useful for somebody. If so - would be nice if you let me know :)


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