Introduce an explicit error value in the Term type

This makes it easier to treat run-time errors (e.g. caused by calls to Predef.error) in a way that is more typical for a lazy functional language.
2011-10-20 14:36:30 +00:00
parent e5accc0d8d
commit ed451653bd
4 changed files with 28 additions and 8 deletions
--- a/src/compiler/GF/Grammar/Grammar.hs
+++ b/src/compiler/GF/Grammar/Grammar.hs
@@ -161,7 +161,7 @@ data Term =

 | Alts Term [(Term, Term)]      -- ^ alternatives by prefix: @pre {t ; s\/c ; ...}@
 | Strs [Term]                   -- ^ conditioning prefix strings: @strs {s ; ...}@
-
+ | Error String                  -- ^ error values returned by Predef.error
  deriving (Show, Eq, Ord)

 data Patt =