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α-wwwiki :: history/evaluator2/20130626-153017.txt

editor : alpha [82.253.3.12] 2013/06/26 15:30:17
_h3 8lines-evaluator{sup 2}

_p Following the previous [[evaluator]], this is another way to integrate the code in the page : the code is written in a container and loaded in a script tag dynamically created. How to use it :
_ul first "init the evaluator", only once,
_ul copy a line from the examples in the code,
_ul paste it into the field below,
_ul then click on the button "evaluate"
_ul and do it again with new values.
{hr}
First {input {@ type="submit" value="init evaluator" onclick="°° 
  var js = document.createElement('script');
  var input = getId('code').innerHTML;
  js.innerHTML = decode_html_entities(input); // < ,>
  document.head.appendChild( js );
  this.value = 'OK, evaluator inited !'; 
  this.disabled='disabled';
°°"}}
 then {input {@ type="submit" value="evaluate" onclick="do_evaluate()"}}
{input {@ id="input" type="texte" value="['sqrt', ['+', ['*',3,3], ['*',4,4]]]" 
  style="width:99%; font:normal 1em courier; color:red;background:#ffc;"}}

{pre {@ id="output"}}

_h3 evaluator's code
{pre {@ id="code"}°°
// 1) evaluator 
var evaluate = function(str) {
  var expression = eval( str ), rest = [];
  if (!Array.isArray(expression)) return expression.toString(); 
  var first = expression.shift();
  if (!dico.hasOwnProperty(first)) return 'Sorry, [' + first + '] is not in dico !';
  expression.map(function(a){rest.push(evaluate(a))})
  return dico[first](rest);
};
// 2) functions dictionary
var dico = {
'+': function(a) { return a.reduce(function(x,y){return Number(x)+Number(y)}) },
'*': function(a) { return a.reduce(function(x,y){return x*y}) },
'-': function(a) { return (a.length == 1)? -a[0]  : a.reduce(function(x,y){return x-y}) },
'/': function(a) { return (a.length == 1)? 1/a[0] : a.reduce(function(x,y){return x/y}) },
'sqrt'  : function(a) { return Math.sqrt( a ) },
'pow'   : function(a) { return Math.pow( a[0], a[1] ) },
'square': function(a) { return a[0]*a[0] },
'hypo'  : function(a) { return Math.sqrt( a[0]*a[0] + a[1]*a[1] ) },
'fac'   : function(a) { return (a< 2)? 1 : a*arguments.callee(a-1); } 
// and so on.
};
// 3) HTML interface
function do_evaluate() {
  getId('output').innerHTML = evaluate( getId('input').value );
}
°°}
_h3 examples
{pre
['+',1,2,3,4,5,6]
['*',1,2,3,4,5,6]
['+', ['*',3,3], ['*',4,4]]
['*', ['+',3,3], ['+',4,4]]
['sqrt', 2]
['pow',2,8]
['sqrt', ['+', ['*',3,3], ['*',4,4]]]
['hypo',3,4]
['fac',6]
}