On Mon, Nov 05, 2001 at 06:47:17AM -0800, Simon Peyton-Jones wrote:

indeed, it's a stream of lexemes that gets passed to L, so there's no whitespace anyway

The report says: The input to L is: * A stream of tokens as specified by the lexical syntax in the Haskell report, with the following additional tokens: immediately before where I suggested "token" be changed to "lexeme". I think I prefer this for a descriptive algorithm as it means you can do things like the figures in section 2.7 (Layout).

| L (t:ts) ms = L ts ms if t is whitespace

Bah, I *really* meant L (t:ts) ms = t : L ts ms if t is whitespace :-) Also, the line L (}:ts) (0:ms) = } : (L ts ms) should be L (}:ts) (m:ms) = } : (L ts ms) if m == 0 = error "Implicit block explicitly closed" otherwise or the } will get allowed through by L (t:ts) ms = t : (L ts ms) So my complete suggested function is: L (t:ts) [] = t : L ts [] if t is whitespace = error "lexeme outside of module contents" otherwise L ({n}:ts) (m:ms) = { : (L ts (n:m:ms)) if n > m = { : } : (L ts (m:ms)) otherwise L (<n>:ts) (m:ms) = ; : (L ts (m:ms)) if m = n = } : (L (<n>:ts) ms) if n < m = L ts (m:ms) otherwise L (t:ts) (m:ms) = } : (L (t:ts) ms) if m /= 0 and parse-error(t) L (}:ts) (m:ms) = } : (L ts ms) if m == 0 = error "Implicit block explicitly closed" otherwise L ({:ts) ms = { : (L ts (0:ms)) L (t:ts) ms = t : (L ts ms) L [] [0] = [] L [] (m:ms) = } : L [] ms if m /= 0 Thanks Ian