Posted move to http://internals.rust-lang.org/t/how-are-negative-int-float-literals-handled-during-lexing-parsing/3120 as per this mailing list's auto reply instructions.
On Wed, Jan 27, 2016 at 5:43 PM, Johan Tibell <johan.tib...@gmail.com> wrote: > I posted it to http://discuss.rust-lang.org/. Thanks! > > On Wed, Jan 27, 2016 at 5:41 PM, Kenneth Adam Miller < > kennethadammil...@gmail.com> wrote: > >> Hey, >> >> Without answering your question, I think you might be better off posting >> your question at reddit.com/r/rust because this mailing list has very >> low participation. >> >> On Wed, Jan 27, 2016 at 11:18 AM, Johan Tibell <johan.tib...@gmail.com> >> wrote: >> >>> Hi! >>> >>> I'm trying to read the compiler code (mostly because I'm curious) and >>> right now I'm trying to understand the handling of negative integer/float >>> literals. >>> >>> In token.rs we have: >>> >>> pub enum Lit { >>> ... >>> Integer(ast::Name), >>> Float(ast::Name), >>> ... >>> } >>> >>> So at this stage these literals are still just (interned) strings. In >>> lexer/mod.rs we can see that the lexer doesn't consume any plus/minus >>> sign, so the above tokens don't contain them. >>> >>> In ast.rs we have: >>> >>> pub enum Expr_ { >>> ... >>> /// A literal (For example: `1u8`, `"foo"`) >>> ExprLit(P<Lit>), >>> ... >>> } >>> >>> pub enum Lit_ { >>> ... >>> /// An integer literal (`1u8`) >>> LitInt(u64, LitIntType), >>> /// A float literal (`1f64` or `1E10f64`) >>> LitFloat(InternedString, FloatTy), >>> /// A float literal without a suffix (`1.0 or 1.0E10`) >>> LitFloatUnsuffixed(InternedString), >>> ... >>> } >>> >>> pub enum Sign { >>> Minus, >>> Plus >>> } >>> >>> pub enum LitIntType { >>> SignedIntLit(IntTy, Sign), >>> UnsignedIntLit(UintTy), >>> UnsuffixedIntLit(Sign) >>> } >>> >>> I'd expect that somewhere in the code we'd construct e.g. an >>> SignedIntLit with a Minus in it, but I cannot find a single place that does >>> this after looking for all uses of ast::Minus ast::SignedIntLit, etc. >>> >>> So my question is, *since the sign isn't lexed together with the >>> literal, how is it eventually added to the literal that's stored in in e.g. >>> ast::LitInt?* >>> >>> -- Johan >>> >>> >>> _______________________________________________ >>> Rust-dev mailing list >>> Rust-dev@mozilla.org >>> https://mail.mozilla.org/listinfo/rust-dev >>> >>> >> >
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