From 63f77395df8d7e78c21437876ce585b01517f0cc Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adamc@hcoop.net>
Date: Thu, 3 Jun 2010 13:04:37 -0400
Subject: Some serious bug-fix work to get HTML example to compile; this
 includes fixing a bug with 'val' patterns in Unnest and the need for more
 local reduction in Especialize

---
 lib/ur/basis.urs |  2 +-
 lib/ur/string.ur | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

(limited to 'lib/ur')

diff --git a/lib/ur/basis.urs b/lib/ur/basis.urs
index 19983cd2..f2dffd38 100644
--- a/lib/ur/basis.urs
+++ b/lib/ur/basis.urs
@@ -79,7 +79,7 @@ val strsub : string -> int -> char
 val strsuffix : string -> int -> string
 val strchr : string -> char -> option string
 val strindex : string -> char -> option int
-val strcspn : string -> string -> option int
+val strcspn : string -> string -> int
 val substring : string -> int -> int -> string
 val str1 : char -> string
 
diff --git a/lib/ur/string.ur b/lib/ur/string.ur
index f19ce174..f7781e01 100644
--- a/lib/ur/string.ur
+++ b/lib/ur/string.ur
@@ -11,7 +11,15 @@ val suffix = Basis.strsuffix
 val index = Basis.strindex
 val atFirst = Basis.strchr
 
-fun mindex {Haystack = s, Needle = chs} = Basis.strcspn s chs
+fun mindex {Haystack = s, Needle = chs} =
+    let
+        val n = Basis.strcspn s chs
+    in
+        if n >= length s then
+            None
+        else
+            Some n
+    end
 
 fun substring s {Start = start, Len = len} = Basis.substring s start len
 
-- 
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