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--- projects:minilisp [2006/02/22 16:08]
leonb created
+++ projects:minilisp [2016/02/17 09:56] (current)
leonb [MiniLisp]
@@ Line 1: / Line 1: @@
-====== Miniexp and Minilisp ======
+====== MiniLisp ======
+{{lambda.jpg?150 }}
+Many years working with [[lush|Lush]] have taken their toll.
+There are many things I really dislike doing in C or C++
+when I know how easy they would be in Lisp.
+The essential lisp data structure is called the S-Expression.
+S-Expressions can represent lots of complicated things
+using a simple printable format.  These are the main
+reason why many people find XML or JSON appealing.
+But I keep returning to S-Expression because they are so much simpler.
+===== MiniExp =====
+At some point I decided to simply write a C++ library
+to handle the basic lisp data structure: [[wp>S-expressions]].
+The implementation fits in a single C++ file,
+including a garbage collector and a pretty printer.
+The full documentation is available as comments in
+the header file ''miniexp.h''
+MiniExp handles four basic types of S-expressions:
+  * Integers, in range [-2<sup>29</sup>...2<sup>29</sup>-1].
+  * Symbols, which are small strings represented by a unique handle.
+  * Pairs, which are the basic components of lists.
+  * Objects, which encapsulate any C++ object derived from class ''miniobj_t''
+Examples:
+  minivar_t a_symbol = miniexp_symbol("foo");
+  minivar_t a_number = miniexp_number(23);
+  minivar_t a_list = miniexp_cons(a_symbol, miniexp_cons(a_number, miniexp_nil));
+  minivar_t an_object = miniexp_string("Strings are implemented as objects.");
+The type of the S-expression is ''miniexp_t''.
+But we often store them into variables of type ''minivar_t''.
+The difference is garbage collection.
+The garbage collector preserves all S-expressions stored in a ''minivar_t''
+and all S-expressions recursively pointed by preserved S-expresssions.
+To print a S-expression, one could write something like:
+  if (miniexp_numberp(exp))
+    printf("%d", miniexp_to_int(exp));
+  else if (miniexp_symbolp(exp))
+    printf("%s", miniexp_to_name(exp));
+  else if (miniexp_consp(exp))
+    ....
+But there is an easier way:
+  miniexp_print(exp);
+and a prettier way:
+  miniexp_pprint(exp, 72);  // 72 is the target number of columns
+You can also read S-expressions from the standard input
+  minivar_t exp = miniexp_read();
+See the documentation in file ''miniexp.h'' for more details.
+===== MiniLisp =====
+During the development of ''miniexp.h'' and ''miniexp.cpp'', it
+appeared that the best way to test s-expressions was to make
+the last step and program a complete lisp interpreter.
+Let's see what it can do:
+  MiniLisp, (C) 2005, Leon Bottou.
+  Available under the GNU General Public Licence.
+   (+ 2 3)
+  = 5
+   (defun (square x) (* x x))
+  = square
+   (square (+ 2 3))
+  = 25
+   (defun (sum l) (if (consp l) (+ (car l) (sum (cdr l))) 0))
+  = sum
+   (sum '(1 8 7 3))
+  = 19
+   (pretty sum)
+  (defun (sum l) (if (consp l) (+ (car l) (sum (cdr l))) 0))
+  = ()
+   (pretty pretty)
+  (defmacro (pretty f)
+  (let ((s (if (symbolp f) (list (list quote f)))))
+    (list (quote let)
+      (list (list (quote s) (list (quote funcdef) f . s)))
+      (list (quote pprint) (quote s) 72)
+      () ) ) )
+  = ()
+The interpreter is very slow because symbol lookup is not optimized.
+But it makes a nice example of using MiniExp.
+===== Download =====
+The most recent MiniExp source code is available from the DjVu Git repository.
+  * [[http://sourceforge.net/p/djvu/djvulibre-git/ci/master/tree/libdjvu/miniexp.h|miniexp.h]]
+  * [[http://sourceforge.net/p/djvu/djvulibre-git/ci/master/tree/libdjvu/miniexp.cpp|miniexp.cpp]]
+The documentation is in file ''miniexp.h''.
+You can also check the MiniLisp source:
+  * [[http://sourceforge.net/p/djvu/djvulibre-git/ci/master/tree/doc/minilisp/|minilisp (tree)]]

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