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|
var parser = new Tokemon({
/**
* this could be done much more simply as
*
* exp : '{primary} sum=( op=["+"|"-"|"*"|"/"] {primary} )*',
* primary : 'int=@integer | neg="-"? "(" exp=exp ")"'
*
* But there's priority operators, as * and ^
* so whenever there's a product, we create a new node.
* It allows to recover the products more simply than just a "linear" search
* There's just to test if the next node has a product, and retrieve the corresponding table
*/
/**
* sum inherits from product for the rightmost symbol
* sum create a nested rule sum.sum, that also inherits from product
* without product inheritance , it gives:
* {primary} product=( op=["*"|"/"] {primary} )* sum=( op=["+"|"-"] {primary} product=( op=["*"|"/"] {primary} )*)*
*/
sum : '{product} sum=( op=@sum {product} )*',
/**
* product inherits from primary for the rightmost symbol
* product create a nested rule product.product , define operators + or - and also inherits it product
* without primary inheritance , it gives:
* int=@integer | neg="-"? "(" exp=sum ")" product=( op=["*"|"/"] int=@integer | neg="-"? "(" exp=sum ")" )*
*/
product : '{primary} product=( op=@product {primary} )*',
// an integer, or a group in parenthesis,
primary : 'number=@number | neg="-"? "(" exp=sum ")"'
},{
sum : ['+', '-'],
product : ['*', '/'],
//the tokenizer return a number through parseFloat
number : [
function (parser, node, input, index, length){
var start = 0,
minlen = 1,
float_ = false,
ch;
input.charCodeAt(index) === 45 && start++ && minlen++;
input.charCodeAt(index + start) === 46 && start++ && (float_ = true);
do{
ch = input.charCodeAt(index + start);
if(ch >= 48 && ch <= 57){
++start ;
continue;
}
if(!float_ && ch === 46 ){
++start ;
minlen = start;
float_ = true;
continue;
}
break;
}
while(true);
return start >= minlen ? input.substr(index, start) : null;
},
parseFloat
],
whitespace : function(parser, node, input, index, length){
var start = 0,
ch;
do{
ch = input.charCodeAt(index + start);
if(ch === 32 || (ch >= 9 && ch <= 13)){
++start ;
continue;
}
break;
}
while(true);
return start ? input.substr(index, start) : null;
}
},
['whitespace'], //skip space
'sum' , //boot rule
false //not case sensitive
); |
