Lexer in D

[Namespace]

I noted it to late: decode comes from readText: readText 
validates your text. I will now  use std.file.read.

The new trace output is here and it seems you're right, isKeyword 
and isType (yes I'd decided to separate it again and keep both in 
the lexer) take a lot of time:
http://dpaste.1azy.net/0d6aff6b
  154874      106186       95403           0     pure nothrow bool 
Puzzle.Lexer.isKeyword(immutable(char)[])
  159688       78020       69289           0     pure nothrow bool 
Puzzle.Lexer.isType(immutable(char)[])

I never thought that. :)