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Replace persistent variable system

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Previous system linked the variable name with the saved value, meaning the variable could not be renamed or moved outside the global scope.

Instead we propose to store all persistent values in a global table, identifying each by a key. To still allow nice manipulation with identifiers, the alias syntax replace the persistent syntax for symbols - an aliases symbol will act as if a function call was used in place of the identifier when it appear.
This commit is contained in:
Étienne Fildadut 2023-12-27 21:25:14 +01:00
parent 56ed6c912b
commit e71bff9562
13 changed files with 169 additions and 58 deletions
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38
ast/Environment.lua
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@ -16,7 +16,11 @@ local VariableMetadata = ast.abstract.Runtime {
self.branched = Branched:new(state, value)
end,
get = function(self, state)
return self.branched:get(state)
if self.symbol.alias then
return self.branched:get(state):call(state, ArgumentTuple:new())
else
return self.branched:get(state)
end
end,
set = function(self, state, value)
assert(not self.symbol.constant, ("trying to change the value of constant %s"):format(self.symbol.string))
@ -24,7 +28,13 @@ local VariableMetadata = ast.abstract.Runtime {
local r = self.symbol.type_check:call(state, ArgumentTuple:new(value))
if not r:truthy() then error(("type check failure for %s; %s does not satisfy %s"):format(self.symbol.string, value, self.symbol.type_check)) end
end
self.branched:set(state, value)
if self.symbol.alias then
local assign_args = ArgumentTuple:new()
assign_args:add_assignment(value)
self.branched:get(state):call(state, assign_args)
else
self.branched:set(state, value)
end
end,
_format = function(self, ...)
@ -108,6 +118,19 @@ local Environment = ast.abstract.Runtime {
self:define(state, symbol, exp)
end
end,
define_alias = function(self, state, symbol, call)
assert(symbol.alias, "symbol is not an alias")
assert(call.type == "call", "alias expression must be a call")
local get = ast.Function:new(ast.ParameterTuple:new(), call):eval(state)
local set_param = ast.ParameterTuple:new()
set_param:insert_assignment(ast.FunctionParameter:new(ast.Identifier:new("value")))
local assign_expr = ast.Call:new(call.func, call.arguments:with_assignment(ast.Identifier:new("value")))
local set = ast.Function:new(set_param, assign_expr):eval(state)
self:define(state, symbol, ast.Overload:new(get, set))
end,
-- returns bool if variable defined in current or parent environment
defined = function(self, state, identifier)
@ -156,17 +179,6 @@ local Environment = ast.abstract.Runtime {
return self:_get_variable(state, identifier):set(state, val)
end,
-- returns a list {[symbol]=val,...} of all persistent variables in the current strict layer
list_persistent = function(self, state)
assert(self.export, "not an export scope layer")
local r = {}
for _, vm in self.variables:iter(state) do
if vm.symbol.persistent then
r[vm.symbol] = vm:get(state)
end
end
return r
end,
-- returns a list {[symbol]=val,...} of all exported variables in the current strict layer
list_exported = function(self, state)
assert(self.export, "not an export scope layer")