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diff --git a/045space_surround.cc b/045space_surround.cc
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--- /dev/null
+++ b/045space_surround.cc
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+//: So far you can have global variables by not setting default-space, and
+//: local variables by setting default-space. You can isolate variables
+//: between those extremes by creating 'surrounding' spaces.
+//:
+//: (Surrounding spaces are like lexical scopes in other languages.)
+
+:(scenario surrounding_space)
+# location 1 in space 1 refers to the space surrounding the default space, here 20.
+recipe main [
+  10:number <- copy 5:literal  # pretend array
+  20:number <- copy 5:literal  # pretend array
+  default-space:address:array:location <- copy 10:literal
+  0:address:array:location/names:dummy <- copy 20:literal  # later layers will explain the /names: property
+  1:number <- copy 32:literal
+  1:number/space:1 <- copy 33:literal
+]
+# chain space
++mem: storing 20 in location 11
+# store to default-space
++mem: storing 32 in location 12
+# store to chained space
++mem: storing 33 in location 22
+
+//: If you think of a space as a collection of variables with a common
+//: lifetime, surrounding allows managing shorter lifetimes inside a longer
+//: one.
+
+:(replace{} "long long int space_base(const reagent& x)")
+long long int space_base(const reagent& x) {
+//?   cerr << "space_base: " << x.to_string() << '\n'; //? 1
+  return space_base(x, space_index(x), Current_routine->calls.front().default_space);
+}
+
+long long int space_base(const reagent& x, long long int space_index, long long int base) {
+//?   trace("foo") << "base of space " << space_index << '\n'; //? 1
+//?   cerr << "space_base sub: " << x.to_string() << '\n'; //? 1
+  if (space_index == 0) {
+//?     trace("foo") << "base of space " << space_index << " is " << base << '\n'; //? 1
+    return base;
+  }
+//?   trace("foo") << "base of space " << space_index << " is " << Memory[base+1] << '\n'; //? 1
+  long long int result = space_base(x, space_index-1, Memory[base+1]);
+  return result;
+}
+
+long long int space_index(const reagent& x) {
+//?   cerr << "space_index: " << x.to_string() << '\n'; //? 1
+  for (long long int i = /*skip name:type*/1; i < SIZE(x.properties); ++i) {
+    if (x.properties.at(i).first == "space") {
+      assert(SIZE(x.properties.at(i).second) == 1);
+      return to_integer(x.properties.at(i).second.at(0));
+    }
+  }
+  return 0;
+}
+
+:(scenario permit_space_as_variable_name)
+recipe main [
+  space:number <- copy 0:literal
+]