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α-wwwiki :: history/lisp/20130713-075530.txt

editor : alpha [82.248.190.27] 2013/07/13 07:55:30
_h1 lisp
_p The [[lambdaway project|../lambdaway_2.0/]] contains two lisp engines :
_ul [[lambdalisp|../lambdaway_2.0/?view=lambdalisp]] which is a true Lisp mini dialect,
_ul [[lambdatalk|../lambdaway_2.0/?view=lambdatalk]] which is built on a different engine (see [[parser]]) and which contains a very basic subset of Lisp, much more oriented for HTML treatments in the wiki.
_p In alphawiki, lambdatalk{sup lite} doesn't try to mimic Lisp, and is nothing then a Javascript wrapper. Let's focus on the function define applied to the factorial :

_h3 1) with lambdalisp
_p Except  brackets replacing parenthesis (to avoid conflicts with simple parenthesis used in the wiki text), it's pure lisp :

{pre °°
[define fac 
   [lambda [n]
      [if [< n 1] 
         1 
         [* n [fac [-- n]]]
      ]
   ]
]
[fac 6]
°°}

_h3 2) with lambdatalk 
_p In the previous version of lambdatalk, arguments must be prefixed by ":", the words "then" and "else" are added (for sugar) in the "if" operator : 
{pre °°
{define fac (:n)
   (if (< :n 1)
        then 1
        else (* :n (fac (-- :n)))
   )
}
{fac 6}
°°}

_h3 3) with lambdatalk (in α-wiki)
_p In α-wiki's reduced version of lambdatalk, the body is any Javascript expression :
{pre °°
{define fac (n)
  function rfac (n) { 
    if (n< 1) 
      return 1;
    else 
      return n*rfac(n-1); 
  } 
  return rfac(n);
}
{fac 6}
°°}
_p See also pages [[define]], [[defun]], [[lambda]] and others like [[recursion]].
_p The question is « Which is the best in a wiki context ? »

_h3 links
_ul [[lml.b9.com/|http://lml.b9.com/]]
_ul [[deptinfo.unice.fr/~roy/progfonc|http://deptinfo.unice.fr/~roy/progfonc.html]]