I'd like to have a function:

@nothrow bool isNumberLitteral(string a);

unittest{

assert(isNumberLitteral("1.2"));

assert(!isNumberLitteral("a1.2"));

assert(!isNumberLitteral("a.b"));

}

I want it nothrow for efficiency (I'm using it intensively), and try/catch as below has significant runtime overhead (esp when the exception is caught):

bool isNumberLitteral(string a){//slow because throws

try{

import std.conv:to;

auto ret=a.to!double;

}

catch

return false;

return true;

}

even this can throw, eg on "a.b" (and uses gc)

bool isNumberLitteral(T=double)(string a){

import std.conv;

//ugly hack to avoid throwing;

if(!a.length||a==".")

return false;

string s="0"~a;

auto x=parse!T(s);

return s.length==0;

}