sparql.rs

macro_rules! select_variables (
    () => {""};
    ($head:ident $($tail:ident)*) => {
        concat!(" ?", stringify!($head), select_variables!($($tail)*));
        };
);

macro_rules! fmt(
    ($a:tt) => {stringify!($a)};
    (?$a:tt) => {concat!("?", stringify!($a))};
    ($ns:ident : $val:ident) => {concat!(stringify!($ns), ":", stringify($val))}
);

macro_rules! opt_whitespace(
    () => {""};
    (.$($tail:tt)*) => {concat!(".\n", next_token!($($tail)*))};
    ($($tail:tt)*) => {concat!(" ", next_token!($($tail)*))};
);

macro_rules! next_token(
    () => {""};
    ($ns:ident : $val:ident $($tail:tt)*) => {concat!(fmt!($ns : $val), opt_whitespace!($($tail)*))};
    (?$var:ident $($tail:tt)*) => {concat!(fmt!(?$var), opt_whitespace!($($tail)*))};
    ($any:tt $($tail:tt)*) => {concat!(fmt!($any), opt_whitespace!($($tail)*))};
);

macro_rules! select(
    ($($var:tt),* where $($statement:tt)*) => {
        concat!(
            "SELECT",
            select_variables!($($var)*),
            "\nWHERE\n",
            next_token!($($statement)*),
            "SERVICE wikibase:label { bd:serviceParam wikibase:language \"en\". }"

        );
    };
);