Numeric read seems too strict

David Feuer david.feuer at
Mon Sep 12 18:03:39 UTC 2016

By the way, I believe we should be able to read numbers more efficiently by
parsing them directly instead of lexing first. We have to deal with
parentheses, white space, and signs uniformly for all number types. Then
specialized foldl'-style code *should* be able to parse integral and
fractional numbers faster than any lex-first scheme.

On Sep 12, 2016 1:53 PM, "David Feuer" <david.feuer at> wrote:

I noticed the other day that

readMaybe (fix ('a':)) :: Maybe Double

is an infinite loop. The problem is that the lexer doesn't know that it's
expected to lex a number. It just keeps scanning and scanning to get to the
end of the endless token. Shall we fix this?
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