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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:integer <- copy 5:literal # pretend array
20:integer <- 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:integer <- copy 32:literal
1:integer/space:1 <- copy 33:literal
]
+run: instruction main/3
+mem: storing 20 in location 11
+run: instruction main/4
+mem: storing 32 in location 12
+run: instruction main/5
+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{} "index_t space_base(const reagent& x)")
index_t space_base(const reagent& x) {
return space_base(x, space_index(x), Current_routine->calls.top().default_space);
}
index_t space_base(const reagent& x, index_t space_index, index_t base) {
//? trace("foo") << "base of space " << space_index << '\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
index_t result = space_base(x, space_index-1, Memory[base+1]);
return result;
}
index_t space_index(const reagent& x) {
for (index_t i = 0; i < x.properties.size(); ++i) {
if (x.properties[i].first == "space")
return to_int(x.properties[i].second[0]);
}
return 0;
}
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