function F_instances_of(needle,haystack){
needle =String(needle);
haystack=String(haystack);
var i=0,t=0;
if(needle!="")
{
while(i<haystack.length && haystack.indexOf(needle,i)>-1)
{
i = haystack.indexOf(needle,i)+1;
t++;
}
}
return(t);
}