start =

expression

expression =

atom

/ listatom

/ nestedlist

validchar

= [0-9a-zA-Z_?!+\-=@#$%^&*/.]

atom =

chars:validchar+

{ return chars.join(""); }

listatom =

"(" space* natom:atom satom:spaceatom* space* ")"

{ if (satom && satom.length) {

satom.unshift(natom);

return satom;

} else {

return [natom];

}

}

nestedlist =

"(" space* natom1:atom* satom1:spaceatom* space* latom1:listatom* space* ")"

{

var result = [];

if (natom1 && natom1.length) {

result = result.concat(natom1);

}

if (satom1 && satom1.length) {

result = result.concat(satom1);

}

if (latom1 && latom1.length) {

result = result.concat(latom1);

}

return result;

}

space =

" "

spaceatom =

space natom:atom

{ return natom; }