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{div {@ class="block"}
_h1 λtalk out of λtank (1|[[2|?view=story2]])

_p {b LT} is a very reduced fork of the [[lambdatalk|?view=coding]]'s engine, working in any HTML document, out of its native wiki environmemnt, [[lambdatank|?view=coding3]].

_p So, in any HTML document, writing

{pre
<{span}pre id="LT_input" contenteditable>

here is any LT code

<{span}/pre>

<{span}div id="LT_output"><{span}/div>

<{span}script>

here is the javascript code
  shown in the fourth column

<{span}/script>
}

_p displays two frames:

_ul 1) An input frame where can be written any valid LT code, see for instance the {b input} column
_ul 2) An output frame displaying the result in real time, see the {b output} column.

_p That's all!

_p {b Note:} Currently modifications to the code can't be saved - except in this wiki page via a transfert inside the page editor, when it's allowed - and a few {i small} bugs are still to be fixed when editing in the contenteditable container. It's a work under construction.

_h2 quick explanation

_p Currently {b LT} comes with two special forms, {b lambda & def}, neither {b if then else} nor {b let var = val} syntactic sugar, and a reduced but extendable set of HTML/CSS, MATH and GRAPHIC primitives.

{prewrap
{b HTML/CSS}
[ '@', 'div', 'span', 'a', 'ul', 'ol', 'li', 'dl', 'dt', 'dd', 'table', 'tr', 'td', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'p', 'b', 'i', 'u', 'center', 'br', 'hr', 'blockquote', 'del', 'sup', 'sub', 'code', 'img', 'pre', 'audio', 'source', 'svg', 'path', 'circle', 'animateMotion', 'mpath' ]

{b MATH}
[ '=', '+', '-', '*', '/', 'sqrt' ]

{b GRAPHIC}
[ 'turtle' ]

... extendable in line
}

_p The implementation of the {b LT} evaluator is constructed in such a way that the special forms {b lambda & def} are evaluated before the other forms, which are evaluated from the inside out.

_p And so, for instance, the following LT code

{pre {@ class="mini"}
(def hypo
 (lambda (:a :b)
  (sqrt (+ (* :a :a) (* :b :b)))
))

(hypo 3 4)
}

_p is evaluated in this order:

_ul 1) the {b lambda} expression is replaced by a function reference, say {b #123}

{pre
(def hypo #123)

(hypo 3 4)
}

_ul 2) the {b def} expression is replaced by the name

{pre
hypo

(hypo 3 4)
}

_ul 3) the application {b (hypo 3 4)} is evaluated from inside out

{pre
0: (hypo 3 4)
1: (#123 3 4)
2: ((lambda (:a :b)
            (sqrt (+ (* :a :a) (* :b :b))))
    3 4)
3: (sqrt (+ (* 3 3) (* 4 4)))
4: (sqrt (+ 9 16))
5: (sqrt 25)
6: 5
}

_p {i Et voilà !}

_p {i alain marty 2022/01/26}

_p [[HN|https://news.ycombinator.com/item?id=30134839]]

}

{div {@ class="block"}
_h1 input

_p You can {b freely edit} the frame below ...

(h3 1. playing with HTML & CSS)

(div 
 (@ style="font:bold 2.0em papyrus;")
 hello world
)

(img
 (@ src="data/amelie_poulain.jpg" 
    width="100%"
)) 
(center amélie poulain (b loves) ze lambada.)

(p I say hello to (b my (i brave) new) (u world).)

(div (@ style="font:normal 4.0em georgia;
               text-align:center;")
λ(sup λ(sup λ(sub λ(sup λ(sub λ(sup λ(sup λ(sub λ(sup λ))))))))))

(pre 
some
   code
      √(span (@ style="border-top:1px solid;") 3(sup 2) + 4(sup 2)) -> 5
)

(table
 (tr (td (b item))
     (td (b quantity))
     (td (b price))
     (td (b quantity*price)))
 (tr (td one)
     (td 123)
     (td 10)
     (td (* 123 10)))
 (tr (td two)
     (td 456)
     (td 100)
     (td (* 456 100)))
 (tr (td three)
     (td 789)
     (td 1000)
     (td (* 789 1000)))
 (tr (td )
     (td )
     (td total)
     (td (b (+ (* 123 10)
               (* 456 100)
               (* 789 1000)))))
)

(p with these CSS rules:)

(pre 
table '{ width:100% }
td '{ padding:5px;
   text-align:right; 
   background:#ddd; 
        color:#f00; 
         font:normal 1.1em courier; 
}
)

(h3 2. playing with maths)

(pre
(* 1 2 3     4 5 6)
(sqrt 2)
(sqrt (+ (* 3 3) (* 4 4)))

(foo a b)  // foo is unknown
(lambda (:a) :a)

((lambda (:a :b) 
 (sqrt (+ (* :a :a) (* :b :b)))) 3 4)
((lambda (:a :b)
         (sqrt
          (+
           (* :a :a) (* :b :b)
         )))
 1 1)

(def φ (/ (+ 1 (sqrt 5)) 2))
(φ)

(def add (lambda (:a :b) (+ :a :b)))
(add 3 4)
)

(h3 3. here we start from nothing)

(pre

(def TRUE (lambda (:a :b) :a))
(def FALSE (lambda (:a :b) :b))
(def IF (lambda (:a :b :c) (:a :b :c)))

(def PAIR (lambda (:a :b :c) (:c :a :b)))
(def LEFT (lambda (:c) (:c TRUE)))
(def RIGHT (lambda (:c) (:c FALSE)))

(def NIL (lambda (:a) TRUE))
(def ISNIL 
 (lambda (:c) (:c (lambda (:a :b) FALSE))))

(def JB (PAIR james bond))
(LEFT (JB))
(RIGHT (JB))
(ISNIL (JB))
(ISNIL NIL)
)

(h3 4. here comes recursion)

(pre
(def L
 (PAIR a
  (PAIR b 
   (PAIR c
    (PAIR d NIL)))))

(def DISP
 (lambda (:l)
  ((IF (ISNIL :l)
   (lambda (:l) )
   (lambda (:l) (LEFT :l) 
                (DISP (RIGHT :l)))) :l)))
(DISP (L))

(def REV (lambda (:l) (_REV.r :l NIL)))
 (def _REV.r
  (lambda (:a :b)
   ((IF (ISNIL :a)
    (lambda (:a :b) :b)
    (lambda (:a :b) (_REV.r (RIGHT :a)
                           (PAIR (LEFT :a) :b))))
   :a :b)))
(DISP (REV (L)))

(def LENGTH (lambda (:l)
 ((IF (ISNIL :l)
  (lambda (:l) 0)
  (lambda (:l) (+ 1 (LENGTH (RIGHT :l))))) :l)))
(LENGTH (L))

(def CONCAT
 (lambda (:a :b)
  ((IF (ISNIL :b)
   (lambda (:a :b) :a)
   (lambda (:a :b) 
    (CONCAT (PAIR (LEFT :b) :a) (RIGHT :b))))
 :a :b)))
(DISP (CONCAT (L) (REV (L))))

(def FAC
 (lambda (:n)
  ((IF (= :n 1)
   (lambda (:n) 1)
   (lambda (:n) (long_mult :n (FAC (- :n 1))))) :n)))
(FAC 6)
(FAC 20)
(pre 
 (@ style="margin:0; padding:0;
           white-space:pre-wrap; 
           word-wrap:break-word;")
(FAC 100)
)

(def SERIE
 (lambda (:a :b :s)
  ((IF (= :a :b)
   (lambda (:a :b :s) (PAIR :a NIL))
   (lambda (:a :b :s) (PAIR :a (SERIE (+ :a :s) :b :s)))) :a :b :s)))

(DISP (SERIE 0 10 2))
(* (DISP (SERIE 1 10 1)))

(def MAP
 (lambda (:f :s)
  ((IF (ISNIL :s)
   (lambda (:f :s) NIL)
   (lambda (:f :s) (PAIR (:f (LEFT :s)) (MAP :f (RIGHT :s))))) :f :s)))
(DISP (MAP (lambda (:i) (* :i :i)) (SERIE 0 20 2)))

(def HANOI          
 (lambda (:n :from :to :via)
  ((IF (= :n 0)
   (lambda (:n :from :to :via) )
   (lambda (:n :from :to :via)
    (HANOI (- :n 1) :from :via :to)
      (br) move :n from tower :from to tower :to 
    (HANOI (- :n 1) :via :to :from) ))
   :n :from :to :via)))
(HANOI 5 A B C)

HILBERT

(def left
 (lambda (:d :n)
  ((IF (= :n 0)
   (lambda (:d :n) )
   (lambda (:d :n) T90      (right :d (- :n 1))
                   M:d T-90 (left  :d (- :n 1))
                   M:d      (left  :d (- :n 1))
                   T-90 M:d (right :d (- :n 1))
                   T90 
   )) :d :n)))
(def right
 (lambda (:d :n)
  ((IF (= :n 0)
   (lambda (:d :n) )
   (lambda (:d :n) T-90    (left  :d (- :n 1))
                   M:d T90 (right :d (- :n 1))
                   M:d     (right :d (- :n 1))
                   T90 M:d (left  :d (- :n 1))
                   T-90
  )) :d :n)))

(svg (@ width="350px" height="350px")
 (path 
 (@ id="spline"
     d="M (turtle 20 20 0 (left 10 5))"  
      fill="transparent" stroke="#fff" stroke-width="1"
 ))
 (circle 
  (@ cx="0" cy="0" r="5" fill="#f00" stroke="#f00")
  (animateMotion 
   (@ dur="100s" repeatCount="indefinite" rotate="auto")
   (mpath (@ xlink:href="#spline"))
 ))
)

MUSIC

(audio
 (@ controls style="width:100%; height:20px;")
 (source
  (@ src="http://b2b3.free.fr/musique/Wiegenlied.m4a" 
 ))
)

... and so on.
)

</pre>

}

{div {@ class="block"}
_h1 output

_p ... and see the evaluation here:
<div id="LT_output">...</div>
}

{div {@ class="block"}

_h1 javascript

_p Here is the content of the {b script} HTML element

{pre °°
// 1) INTERFACE

setTimeout( 
 function() {
  LT_run();
  document.getElementById('LT_input').addEventListener ( 
   'keyup', function() { LT_run() } ) 
 }, 1 );

var LT_run = function () {
  var s = document.getElementById('LT_input').innerText,
    bal = MINI.balance(s);
  document.getElementById('LT_output').innerHTML =
    (bal.left === bal.right) 
    ? MINI.evaluate( s ) 
    : '< center>unbalanced expressions: (' + 
         bal.left + '|' + bal.right + ')< /center>'
};

// 2) EVALUATION

var MINI = (function() {

var DICT = {};
  var regexp = /$([^\s()]*)(?:[\s]*)([^()]*)$/g;

var evaluate = function(s) {
    s = eval_lambdas(s);
    s = eval_defs(s);
    s = eval_applications(s);
    return s
  };

var eval_applications = function(s) { // nested (first rest)
    while (s !== (s = s.replace(regexp, eval_application)));
    return s;
  };

var eval_lambdas = function(s) {
    while (s !== (s = s.replace(catch_abstraction(s,"lambda"), eval_lambda)));
    return s
  };

var eval_defs = function(s) {
    while (s !== (s = s.replace(catch_abstraction(s,"def"), eval_def)));
    return s   
  };

var eval_application = function() {
    var f = arguments[1] || "", r = arguments[2] || "";
    return DICT.hasOwnProperty(f)?
           DICT[f].apply(null, [r]) : "[" + f + " " + r + "]";
  };

var catch_abstraction = function(s,symb) {  // "... (symbol ...) ..."
    var start = s.indexOf("("+symb);
    if (start == -1) return "none";  
    var nb = 1, index = start; 
    while (nb > 0) {
      index++; if (index > 10000) return "oops catch_index"
           if (s.charAt(index) == "(") nb++;
      else if (s.charAt(index) == ")") nb--; 
    } 
    return s.substring(start, index+1)        //     "(symbol ...)"
  }; 
 
  var eval_lambda = function(s) {     // "(lambda (args) body)"
         s = s.trim()
              .replace(/\s+/g, " ")
              .substring(8)           // "(lambda "
              .replace( /\)$/, ""),   //         "(args) body"
     index = s.indexOf(")"),
    argStr = s.substring(1, index).trim(),
      args = argStr === "" ? [] : argStr.split(" "),
      body = s.substring( argStr.length+2 ).trim(),
      name = "#" + Math.random();

body = eval_lambdas(body);

DICT[name] = function() {
      var valStr = arguments[0].trim().replace(/\s+/g, " "),
            vals = valStr === "" ? [] : valStr.split(" "),
             bod = body.trim();
      if (vals.length < args.length) {          // 1) partial call
          for (var i = 0; i < vals.length; i++)
            bod = bod.replace(RegExp(args[i], "g"), vals[i]);
          var _args_ = args.slice(vals.length).join(" ");
          bod = eval_lambda("(lambda (" + _args_ + ") " + bod + ")");
      } else if (vals.length === args.length) { // 2) total call
          for (var i=0; i < args.length; i++)
            bod = bod.replace( RegExp(args[i], "g"), vals[i] );
      } else {                                  // 3) extra -> the last one
          var _vals_ = vals.slice(0,args.length);
          _vals_[args.length-1] = vals.slice(args.length-1,vals.length).join(' ');
          for (var i=0; i < args.length; i++)
            bod = bod.replace( RegExp(args[i], "g"), _vals_[i] ); 
      } 
      return eval_applications(bod); 
    };

return name
  };

var eval_def = function(s) {       // "(def name body)"
         s = s.trim()
              .replace(/\s+/g, " ")
              .substring(5)          // "(def "
              .replace( /\)$/, ""),  //      "name body"
     index = s.indexOf(" "),
      name = s.substring(0, index).trim(),
      body = s.substring(index).trim();

body = eval_defs(body);

if (body.charAt(0) === "#") {
      DICT[name] = DICT[body];
    } else {
      body = eval_applications(body);
      DICT[name] = function() {
        return body;
      };
    }
    return (name.charAt(0) === "_")? "" : name  
  };

var balance = function(s) {
    var strt = s.match(/$/g),
        stop = s.match(/$/g);
    strt = strt ? strt.length : 0;
    stop = stop ? stop.length : 0;
    return { left:strt, right:stop };
  };

// and so on ...

return { evaluate, balance, DICT }

})();  // en MINI

// 3) DICTIONARY

// HTML/CSS

var htmltags = [ 
'div', 'span', 'a', 'ul', 'ol', 'li', 'dl', 'dt', 'dd', 
'table', 'tr', 'td', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 
'p', 'b', 'i', 'u', 'center', 'br', 'hr', 'blockquote', 
'del', 'sup', 'sub', 'code', 'img', 'pre', 
'audio', 'source', 'svg', 'path' ];

MINI.DICT['@'] = function() { return '@@' + arguments[0].trim() + '@@' } ;

for (var i=0; i< htmltags.length; i++) {        // (div (@ attributs)texte)
  MINI.DICT[htmltags[i]] = function(tag) {      // tag = div
    return function() {                         
      var args = arguments[0].trim();           // args = @@attributs@@texte
      var attr = args.match( /@@[\s\S]*?@@/ );  // attr[0] = @@attributs@@
      if (attr == null) {                       
        return '< '+tag+'>'+args+'< /'+tag+'>';  
      } else {
        args = args.replace( attr[0], '' ).trim();             
        attr = attr[0].replace(/^@@/, '').replace(/@@$/, '');  
        return '< '+tag+' '+attr+'>'+args+'< /'+tag+'>';       
      }
    } 
  }(htmltags[i]);
}

// MATH

MINI.DICT["="] = function() {
    var a = arguments[0].trim().replace(/\s+/g, " ").split(" ");
    return (a[0] === a[1])? 'TRUE' : 'FALSE'
};

MINI.DICT['+'] = function() {
  return arguments[0].trim().replace(/\s+/g, " ").split(' ')
                     .reduce( (a,b) => Number(a)+Number(b) , 0 ) }; 
MINI.DICT['*'] = function() { 
  return arguments[0].trim().replace(/\s+/g, " ").split(' ')
                     .reduce( (a,b) => a*b , 1 ) };

MINI.DICT['-'] = function() { 
  var args = arguments[0].trim().replace(/\s+/g, " ").split(' ');
  return args[0]-args[1] 
}; 
MINI.DICT['/'] = function() { 
  var args = arguments[0].trim().replace(/\s+/g, " ").split(' ');
  return args[0]/args[1] 
};

MINI.DICT['sqrt'] = function() { 
  return Math.sqrt( arguments[0].trim() ) };

MINI.DICT['long_add'] = function () {
  var args = arguments[0].trim().replace(/\s+/g, " ").split(' '),
         a = args[0].split("").reverse(),
         b = args[1].split("").reverse(),
         n = Math.max(a.length, b.length), 
         c = [], 
         d = 0;
  for (var i=0; i < n; i++) {
    c[i] = (a[i] | 0) + (b[i] | 0) + d;
    if (c[i] > 9) {
      c[i] -= 10;
      d = 1;
    } else {
      d = 0;
    }
  } 
  if (d === 1) c.push(1);
  return c.reverse().join('') 
};

MINI.DICT['long_mult'] = function () {
  var args = arguments[0].trim().replace(/\s+/g, " ").split(' '),
         a = args[0].split("").reverse(),
         b = args[1].split("").reverse(),
         c = [];
  for ( var i1 = 0; i1 < a.length; i1++ ) {
    for ( var i2 = 0; i2 < b.length; i2++ ) {
      var j = i1 + i2;
      c[j] = a[i1] * b[i2] + (c[j] | 0);
      if ( c[j] > 9 ) { 
        var f = Math.floor( c[j] / 10 );
        c[j] -= f * 10;
        c[j+1] = f + (c[j+1] | 0);
      }
    }   
  }
  return c.reverse().join("")
};

MINI.DICT['turtle'] = function () {
  var draw = function(str) { // {turtle x0 y0 a0 M100 T90 M50 T-45 ...}
    var args = str.split(' ');
    var x0 = parseFloat(args[0]),
        y0 = parseFloat(args[1]),
        a0 = parseFloat(args[2]),
        poly = [];
    poly.push( [x0, y0, a0] );
    for (var i=3; i < args.length; i++) {
      var act = args[i].charAt(0),
          val = parseFloat(args[i].substring(1));
      if (act === 'M') {
        var p = poly[poly.length-1],
            a = p[2] * Math.PI / 180.0,
            x = p[0] + val * Math.sin(a),
            y = p[1] + val * Math.cos(a);
        poly.push( [x,y,p[2]] )
      } else {
        var p = poly.pop();
        poly.push( [p[0],p[1],p[2]+val] ) 
      }
    }
    for (var pol = '', i=0; i < poly.length; i++)
      pol += Math.round(poly[i][0]) + ' ' +  Math.round(poly[i][1]) + ' ';
    return pol
  };
  return draw( arguments[0].trim().replace(/\s+/g, " ") ); 
};

// and so on ...
 
°°}
}

{script

// INTERFACE

var LT_run = function () {
  var s = document.getElementById('LT_input').innerText,
    bal = MINI.balance(s);
  document.getElementById('LT_output').innerHTML =
    (bal.left === bal.right) 
    ? MINI.evaluate( s ) 
    : '<center>unbalanced expressions: (' + bal.left + '|' + bal.right + ')</center>'
};

setTimeout( 
 function() {
  LT_run();
  document.getElementById('LT_input').addEventListener ( 
   'keyup', function() { LT_run() } ) 
 }, 1 );

// EVAL

var MINI = (function() {

var DICT = {};
  var regexp = /$([^\s()]*)(?:[\s]*)([^()]*)$/g;

var evaluate = function(s) {
    s = eval_lambdas(s);
    s = eval_defs(s);
    s = eval_applications(s);
    return s
  };

var eval_applications = function(s) { // nested (first rest)
    while (s !== (s = s.replace(regexp, eval_application)));
    return s;
  };

var eval_application = function() {
    var f = arguments[1] || "", r = arguments[2] || "";
    return DICT.hasOwnProperty(f)?
           DICT[f].apply(null, [r]) : "[" + f + " " + r + "]";
  };

var eval_lambdas = function(s) {
    while (s !== (s = s.replace(catch_abstraction(s,"lambda"), eval_lambda)));
    return s
  };

var eval_defs = function(s) {
    while (s !== (s = s.replace(catch_abstraction(s,"def"), eval_def)));
    return s   
  };

var catch_abstraction = function(s,symb) {
    var start = s.indexOf("("+symb);
    if (start == -1) return "none";  
    var nb = 1, index = start; 
    while (nb > 0) {
      index++; if (index > 10000) return "oops catch_index"
           if (s.charAt(index) == "(") nb++;
      else if (s.charAt(index) == ")") nb--; 
    } 
    return s.substring(start, index+1)     
  }; 
 
  var eval_lambda = function(s) {       // "(lambda (args) body)"
    s = s.trim()
         .replace(/\s+/g, " ")
         .substring(8)                  // "(lambda "
         .replace( /\)$/, "");          //         "(args) body"
    var index = s.indexOf(")"),
       argStr = s.substring(1, index).trim(),
         args = argStr === "" ? [] : argStr.split(" "),
         body = s.substring( argStr.length+2 ).trim(),
         name = "#" + Math.random();

body = eval_lambdas(body);

return name
  };

var eval_def = function(s) {     // "(def name body)"
    s = s.trim()
         .replace(/\s+/g, " ")
         .substring(5)             // "(def "
         .replace( /\)$/, "");     //      "name body"
    var index = s.indexOf(" ");
    var name = s.substring(0, index).trim();
    var body = s.substring(index).trim();

body = eval_defs(body);

return { DICT, evaluate, balance }

})();  // en MINI

// DICTIONARY

MINI.DICT['@'] = function() { return '@@' + arguments[0].trim() + '@@' } ;

for (var i=0; i< htmltags.length; i++) {        // (div (@ attributs)texte)
  MINI.DICT[htmltags[i]] = function(tag) {      // tag = div
    return function() {                         
      var args = arguments[0].trim();           // args = @@attributs@@texte, don't supertrim for pre
      var attr = args.match( /@@[\s\S]*?@@/ );  // attr[0] = @@attributs@@
      if (attr == null) {                       // args = texte
        return '<'+tag+'>'+args+'</'+tag+'>';   // <div>texte</div>
      } else {
        args = args.replace( attr[0], '' ).trim();             // args = texte
        attr = attr[0].replace(/^@@/, '').replace(/@@$/, '');  // attr = attributs
        return '<'+tag+' '+attr+'>'+args+'</'+tag+'>';         // <div attributs>texte</div>
      }
    } 
  }(htmltags[i]);
}

// {S.reduce {lambda {x y} {* x y}} {S.serie 1 6}}

MINI.DICT["="] = function() {
    var a = arguments[0].trim().replace(/\s+/g, " ").split(" ");
    return (a[0] === a[1])? 'TRUE' : 'FALSE'
};
 
MINI.DICT['+'] = function() {
  return arguments[0].trim().replace(/\s+/g, " ").split(' ').reduce( (a,b) => Number(a)+Number(b) , 0 ) }; 
MINI.DICT['*'] = function() { 
  return arguments[0].trim().replace(/\s+/g, " ").split(' ').reduce( (a,b) => a*b , 1 ) };

MINI.DICT['sqrt'] = function() { 
  return Math.sqrt( arguments[0].trim() ) };

// and so on ...
}

{style 
body { background:#444; }
#page_frame, #page_content, .page_menu {
 background:transparent; 
 color:#fff;
 border:0; box-shadow:0 0 0; 
}
#page_frame { margin-left:0; width:600px; }  
#page_content { width:1700px; }
pre {
 position:relative; z-index:1;  
 overflow-x: scroll;
 padding:10px;
 background:#555; color:#fff; 
}
.block {
 display:inline-block;
 width:380px;
 height:2000px;
 vertical-align:top;
 padding:5px;
 overflow-x:scroll;
}
table { width:100% }
td { text-align:right; background:#ddd; color:#f00; padding:5px; font:normal 1.1em courier; }
.mini { box-shadow:0 0 0; background:#444; color:#fff; margin: 0 0 -10px 0; opacity:0.5}
.mini:hover { opacity:1; }

}