 |
lua-l archive |
|
|
||
|
One of the issues I ran into is with function captures and folding
captures. As discussed earlier [3], it is to be expected, but I still
find it counterintuitive. Consider this simple example:
local lpeg = require('lpeg')
local grammar = { "Sum";
Number = lpeg.R"09"^1 / tonumber;
List = lpeg.V("Number") * ("," * lpeg.V("Number"))^0
/ function(...) print(select('#', ...)) return ... end;
Sum = lpeg.Cf(lpeg.V("List"),
function(acc, newvalue) return newvalue and acc + newvalue end);
}
print(lpeg.match(lpeg.P(grammar),"10,30,43"))
This prints "3\n10" as while the function capture for the List rule
gets three value (as there are three captures), there is no way to
return them as three captures; even when the function returns three
elements, they are seen by Cf() as one capture (so only the first
value is used). I think multiple values returned by function captures
need to be applied as the list of captures instead of one capture with
multiple values.