Ruby STL container setting slices fixes

Setting an STL container wrapper slice better matches the way Ruby
arrays work. The behaviour is now the same as Ruby arrays. The only
exception is the default value used when expanding a container
cannot be nil as this is not a valid type/value for C++ container
elements.

Examples/test-suite/ruby/li_std_vector_runme.rb

@@ -109,7 +109,7 @@ end
 def compare_sequences(a, b)
     if a != nil && b != nil
       if a.size != b.size
-          failed(a, b, "different sizes")
+        failed(a, b, "different sizes")
       end
       for i in 0..a.size-1
         failed(a, b, "elements are different") if a[i] != b[i]
@@ -121,9 +121,26 @@ def compare_sequences(a, b)
     end
 end
 
+def compare_expanded_sequences(a, b)
+    # a can contain nil elements which indicate additional elements
+    # b won't contain nil for additional elements
+    if a != nil && b != nil
+      if a.size != b.size
+        failed(a, b, "different sizes")
+      end
+      for i in 0..a.size-1
+        failed(a, b, "elements are different") if a[i] != b[i] && a[i] != nil
+      end
+    else
+      unless a == nil && b == nil
+        failed(a, b, "only one of the sequences is nil")
+      end
+    end
+end
+
 def check_slice(i, length)
-  aa = [0,1,2,3]
-  iv = IntVector.new([0,1,2,3])
+  aa = [1,2,3,4]
+  iv = IntVector.new(aa)
 
   aa_slice = aa[i, length]
   iv_slice = iv[i, length]
@@ -135,8 +152,8 @@ def check_slice(i, length)
 end
 
 def check_range(i, j)
-  aa = [0,1,2,3]
-  iv = IntVector.new([0,1,2,3])
+  aa = [1,2,3,4]
+  iv = IntVector.new(aa)
 
   aa_range = aa[i..j]
   iv_range = iv[i..j]
@@ -147,6 +164,21 @@ def check_range(i, j)
   compare_sequences(aa_range, iv_range)
 end
 
+def set_slice(i, length, expect_nil_expanded_elements)
+  aa = [1,2,3,4]
+  iv = IntVector.new(aa)
+  aa_new = [8, 9]
+  iv_new = IntVector.new(aa_new)
+
+  aa[i, length] = aa_new
+  iv[i, length] = iv_new
+  if expect_nil_expanded_elements
+    compare_expanded_sequences(aa, iv)
+  else
+    compare_sequences(aa, iv)
+  end
+end
+
 for i in -5..5
   for length in -5..5
     check_slice(i, length)
@@ -159,6 +191,18 @@ for i in -5..5
   end
 end
 
+for i in -4..4
+  for length in 0..4
+    set_slice(i, length, false)
+  end
+end
+
+for i in [5, 6]
+  for length in 0..5
+    set_slice(i, length, true)
+  end
+end
+
 
 dv = DoubleVector.new(10)