3972 - drop ancient experiment for global variables

We never ended up using this, and all it has provided is a hole in the
type system.

Java's lesson is that globals are not essential. Any program that uses
globals can be rewritten to do without them. Just thread a world object
through the program, saving global state in it, and extracting relevant
bits of global state to pass into functions lower down the call chain.

Thanks Andrew Owen for the conversation that led me to focus on this
issue.

1 files changed, 0 insertions, 82 deletions

diff --git a/046global.cc b/046global.cc
deleted file mode 100644
index 9d690806..00000000
--- a/046global.cc
+++ /dev/null
@@ -1,82 +0,0 @@
-//: So far we have local variables, and we can nest local variables of short
-//: lifetimes inside longer ones. Now let's support 'global' variables that
-//: last for the life of a routine. If we create multiple routines they won't
-//: have access to each other's globals.
-//:
-//: This feature is still experimental and half-baked. You can't name global
-//: variables, and they don't get checked for types (the only known hole in
-//: the type system, can cause memory corruption). We might fix these issues
-//: if we ever use globals. Or we might just drop the feature entirely.
-//: [tag: todo]
-
-:(scenario global_space)
-def main [
-  # pretend address:array:location; in practice we'll use new
-  10:num <- copy 0  # refcount
-  11:num <- copy 5  # length
-  # pretend address:array:location; in practice we'll use new
-  20:num <- copy 0  # refcount
-  21:num <- copy 5  # length
-  # actual start of this recipe
-  global-space:space <- copy 20/unsafe
-  default-space:space <- copy 10/unsafe
-  1:num <- copy 23
-  1:num/space:global <- copy 24
-]
-# store to default space: 10 + (skip refcount and length) 2 + (index) 1
-+mem: storing 23 in location 13
-# store to chained space: (contents of location 12) 20 + (refcount and length) 2 + (index) 1
-+mem: storing 24 in location 23
-
-//: to support it, create another special variable called global space
-:(before "End is_disqualified Special-cases")
-if (x.name == "global-space")
-  x.initialized = true;
-:(before "End is_special_name Special-cases")
-if (s == "global-space") return true;
-
-//: writes to this variable go to a field in the current routine
-:(before "End routine Fields")
-int global_space;
-:(before "End routine Constructor")
-global_space = 0;
-:(after "Begin Preprocess write_memory(x, data)")
-if (x.name == "global-space") {
-  if (!scalar(data) || !is_space(x))
-    raise << maybe(current_recipe_name()) << "'global-space' should be of type address:array:location, but tried to write '" << to_string(x.type) << "'\n" << end();
-  if (Current_routine->global_space)
-    raise << "routine already has a global-space; you can't over-write your globals" << end();
-  Current_routine->global_space = data.at(0);
-  return;
-}
-
-//: now marking variables as /space:global looks them up inside this field
-:(after "int space_base(const reagent& x)")
-  if (is_global(x)) {
-    if (!Current_routine->global_space)
-      raise << "routine has no global space\n" << end();
-    return Current_routine->global_space + /*skip refcount*/1;
-  }
-
-//: for now let's not bother giving global variables names.
-//: don't want to make them too comfortable to use.
-
-:(scenario global_space_with_names)
-def main [
-  global-space:space <- new location:type, 10
-  x:num <- copy 23
-  1:num/space:global <- copy 24
-]
-# don't complain about mixing numeric addresses and names
-$error: 0
-
-:(after "bool is_numeric_location(const reagent& x)")
-  if (is_global(x)) return false;
-
-//: helpers
-
-:(code)
-bool is_global(const reagent& x) {
-  string_tree* s = property(x, "space");
-  return s && s->atom && s->value == "global";
-}