diff --git a/arrays.scad b/arrays.scad
index 3e67724..bf236ce 100644
--- a/arrays.scad
+++ b/arrays.scad
@@ -1796,6 +1796,39 @@ function array_group(v, cnt=2, dflt=0) =
     [for (i = [0:cnt:len(v)-1]) [for (j = [0:1:cnt-1]) default(v[i+j], dflt)]];
 
 
+// Function: group_data()
+// Usage:
+//   groupings = group_data(groups, values);
+// Topics: Array Handling
+// See Also: zip(), zip_long(), array_group()
+// Description:
+//   Given a list of integer group numbers, and an equal-length list of values,
+//   returns a list of groups with the values sorted into the corresponding groups.
+//   Ie: if you have a groups index list of [2,3,2] and values of ["A","B","C"], then
+//   the values "A" and "C" will be put in group 2, and "B" will be in group 3.
+//   Groups that have no values grouped into them will be an empty list.  So the
+//   above would return [[], [], ["A","C"], ["B"]]
+// Arguments:
+//   groups = A list of integer group index numbers.
+//   values = A list of values to sort into groups.
+// Example:
+//   groups = group_data([1,2,0], ["A","B","C"]);  // Returns [["B"],["C"],["A"]]
+// Example:
+//   groups = group_data([1,3,1], ["A","B","C"]);  // Returns [[],["A","C"],[],["B"]]
+function group_data(groups, values) =
+    assert(all_integer(groups) && all_nonnegative(groups));
+    assert(is_list(values));
+    assert(len(groups)==len(values),
+           "The groups and values arguments should be lists of matching length.")
+    let( sorted = _group_sort_by_index(zip(groups,values),0) )
+    // retrieve values and insert []
+    [for(i=idx(sorted))
+       let( a  = i==0? 0 : sorted[i-1][0][0]+1,
+            g0 = sorted[i] )
+       each [ for(j=[a:1:g0[0][0]-1]) [], [for(g1=g0) g1[1]] ]
+    ];
+
+
 // Function: flatten()
 // Usage:
 //   list = flatten(l);
diff --git a/common.scad b/common.scad
index 62c83ad..9ffade5 100644
--- a/common.scad
+++ b/common.scad
@@ -578,6 +578,7 @@ module no_module() {
 
 function _valstr(x) =
     is_list(x)? str("[",str_join([for (xx=x) _valstr(xx)],","),"]") :
+    is_num(x) && x==floor(x)? fmt_int(x) :
     is_finite(x)? fmt_float(x,12) : x;
 
 
diff --git a/math.scad b/math.scad
index 764cdc5..319f449 100644
--- a/math.scad
+++ b/math.scad
@@ -1204,6 +1204,31 @@ function all_equal(vec,eps=0) =
    eps==0 ? [for(v=vec) if (v!=vec[0]) v] == []
           : [for(v=vec) if (!approx(v,vec[0])) v] == [];
 
+
+// Function: all_integer()
+// Usage:
+//   bool = all_integer(x);
+// Description:
+//   If given a number, returns true if the number is a finite integer.
+//   If given an empty list, returns false.  If given a non-empty list, returns
+//   true if every item of the list is an integer.  Otherwise, returns false.
+// Arguments:
+//   x = The value to check.
+// Examples:
+//   b = all_integer(true);  // Returns: false
+//   b = all_integer("foo"); // Returns: false
+//   b = all_integer(4);     // Returns: true
+//   b = all_integer(4.5);   // Returns: false
+//   b = all_integer([]);    // Returns: false
+//   b = all_integer([3,4,5]);   // Returns: true
+//   b = all_integer([3,4.2,5]); // Returns: false
+//   b = all_integer([3,[4,7],5]); // Returns: false
+function all_integer(x) =
+    is_num(x)? is_int(x) :
+    is_list(x)? (x != [] && [for (xx=x) if(!is_int(xx)) 1] == []) :
+    false;
+
+
 // Function: approx()
 // Usage:
 //   b = approx(a,b,[eps])