Substring functions; fix a nasty MonoReduce pattern match substitution bug

4 files changed, 38 insertions, 0 deletions

diff --git a/lib/js/urweb.js b/lib/js/urweb.js
index db3c934c..be3d652a 100644
--- a/lib/js/urweb.js
+++ b/lib/js/urweb.js
@@ -353,6 +353,23 @@ function bs(b) { return (b ? "True" : "False") }
 function sub(s, i) { return s[i]; }
 function suf(s, i) { return s.substring(i); }
 function slen(s) { return s.length; }
+function sidx(s, ch) {
+  var r = s.indexOf(ch);
+  if (r == -1)
+    return null;
+  else
+    return r;
+}
+function schr(s, ch) {
+  var r = s.indexOf(ch);
+  if (r == -1)
+    return null;
+  else
+    return s.substring(r);
+}
+function ssub(s, start, len) {
+  return s.substring(start, start+len);
+}
 
 function pi(s) {
   var r = parseInt(s);
diff --git a/lib/ur/basis.urs b/lib/ur/basis.urs
index c63c5ed4..d70ccc24 100644
--- a/lib/ur/basis.urs
+++ b/lib/ur/basis.urs
@@ -57,6 +57,9 @@ val strlen : string -> int
 val strcat : string -> string -> string
 val strsub : string -> int -> char
 val strsuffix : string -> int -> string
+val strchr : string -> char -> option string
+val strindex : string -> char -> option int
+val substring : string -> int -> int -> string
 
 class show
 val show : t ::: Type -> show t -> t -> string
diff --git a/lib/ur/string.ur b/lib/ur/string.ur
index 23670966..e6d5903e 100644
--- a/lib/ur/string.ur
+++ b/lib/ur/string.ur
@@ -5,3 +5,14 @@ val append = Basis.strcat
 
 val sub = Basis.strsub
 val suffix = Basis.strsuffix
+
+val index = Basis.strindex
+val atFirst = Basis.strchr
+
+fun substring s {Start = start, Len = len} = Basis.substring s start len
+
+fun split s ch =
+    case index s ch of
+        None => None
+      | Some i => Some (substring s {Start = 0, Len = i},
+                        substring s {Start = i + 1, Len = length s - i - 1})
diff --git a/lib/ur/string.urs b/lib/ur/string.urs
index ef522387..097a423f 100644
--- a/lib/ur/string.urs
+++ b/lib/ur/string.urs
@@ -6,3 +6,10 @@ val append : t -> t -> t
 
 val sub : t -> int -> char
 val suffix : t -> int -> string
+
+val index : t -> char -> option int
+val atFirst : t -> char -> option string
+
+val substring : t -> {Start : int, Len : int} -> string
+
+val split : t -> char -> option (string * string)