Implement lax substr()

lib/Builtins.cs

@@ -3,6 +3,22 @@
 using System.Collections.Generic;
 
 public class Builtins {
+    public static string LaxSubstring(string str, int from) {
+        if (from <= 0)
+            return str;
+        if (from >= str.Length)
+            return "";
+        return str.Substring(from);
+    }
+
+    public static string LaxSubstring2(string str, int from, int l) {
+        if (from <= 0) from = 0;
+        if (from >= str.Length) from = str.Length;
+        if (l >= str.Length - from) l = str.Length - from;
+        if (l < 0) l = 0;
+        return str.Substring(from, l);
+    }
+
     public static Variable NumericEq(Variable v1, Variable v2) {
         IP6 o1 = v1.Fetch();
         IP6 o2 = v2.Fetch();

src/CgOp.pm

@@ -163,7 +163,7 @@ use warnings;
 
     sub num_to_string { rawcall($_[0], 'ToString') }
     sub str_length { getfield('Length', $_[0]) }
-    sub str_substring { rawcall($_[0], 'Substring', $_[1], $_[2]) }
+    sub str_substring { rawscall('Builtins.LaxSubstring2:m,String', @_) }
     sub str_chr { rawnew('str', cast('clr:System.Char', $_[0]), CgOp::int(1)) }
     sub strcmp { rawscall('String.CompareOrdinal', $_[0], $_[1]) }
     sub str_tolower { rawcall($_[0], 'ToLowerInvariant:m,String') }

test2.pl

@@ -19,6 +19,9 @@
     my $died = 1;
     try { $*NONEX = 1; $died = 0; }
     ok $died, "Assignment to non-existing dynvar fails";
+
+    is "foo".substr(5,2), "", "substr starting off end works";
+    is "foo".substr(1,10), "oo", "substr ending off end works";
 }
 
 #is $?FILE, 'test.pl', '$?FILE works';