[language] replace constant symbols with a constant value check function

anselme/ast/Environment.lua

@@ -31,12 +31,9 @@ local VariableMetadata = ast.abstract.Runtime {
 		return self.symbol
 	end,
 	set = function(self, state, value)
-		if self.symbol.constant then
-			error(("trying to change the value of constant %s"):format(self.symbol.string:format(state)), 0)
-		end
 		if self.symbol.value_check then
 			local r = self.symbol.value_check:call(state, ArgumentTuple:new(value))
-			if not r:truthy() then error(("value check failure for %s; %s does not satisfy %s"):format(self.symbol.string:format(state), value, self.symbol.value_check:format(state)), 0) end
+			if not r:truthy() then error(("can not set %s = %s; %s value check failed"):format(self.symbol.string:format(state), value, self.symbol.value_check:format_short(state)), 0) end
 		end
 		if self.symbol.alias then
 			local assign_args = ArgumentTuple:new()

anselme/ast/Symbol.lua

@@ -8,7 +8,6 @@ Symbol = ast.abstract.Node {
 	type = "symbol",
 
 	string = nil,
-	constant = nil, -- bool
 	alias = nil, -- bool
 	exported = nil, -- bool
 	value_check = nil, -- exp
@@ -18,7 +17,6 @@ Symbol = ast.abstract.Node {
 	init = function(self, str, modifiers)
 		modifiers = modifiers or {}
 		self.string = str
-		self.constant = modifiers.constant
 		self.value_check = modifiers.value_check
 		self.alias = modifiers.alias
 		self.confined_to_branch = modifiers.confined_to_branch
@@ -26,7 +24,7 @@ Symbol = ast.abstract.Node {
 	end,
 	with = function(self, modifiers)
 		modifiers = modifiers or {}
-		for _, k in ipairs{"constant", "value_check", "alias", "exported", "confined_to_branch"} do
+		for _, k in ipairs{"value_check", "alias", "exported", "confined_to_branch"} do
 			if modifiers[k] == nil then
 				modifiers[k] = self[k]
 			end
@@ -48,9 +46,6 @@ Symbol = ast.abstract.Node {
 
 	_hash = function(self)
 		local prefix = ""
-		if self.constant then
-			prefix = prefix .. ":"
-		end
 		if self.alias then
 			prefix = prefix .. "&"
 		end
@@ -66,9 +61,6 @@ Symbol = ast.abstract.Node {
 
 	_format = function(self, state, prio, ...)
 		local s = ":"
-		if self.constant then
-			s = s .. ":"
-		end
 		if self.alias then
 			s = s .. "&"
 		end

anselme/parser/expression/primary/function_definition.lua

@@ -159,19 +159,18 @@ end
 
 return primary {
 	match = function(self, str)
-		return str:match("^%::?&?@?%$")
+		return str:match("^%:&?@?%$")
 	end,
 
 	parse = function(self, source, options, str)
 		local source_start = source:clone()
-		local mod_const, mod_alias, mod_exported, rem = source:consume(str:match("^(%:(:?)(&?)(@?)%$)(.-)$"))
+		local mod_alias, mod_exported, rem = source:consume(str:match("^(%:(&?)(@?)%$)(.-)$"))
 
 		-- get modifiers
-		local constant, exported, alias
-		if mod_const == ":" then constant = true end
+		local exported, alias
 		if mod_alias == "&" then alias = true end
 		if mod_exported == "@" then exported = true end
-		local modifiers = { constant = constant, exported = exported, alias = alias }
+		local modifiers = { exported = exported, alias = alias }
 
 		-- search for a valid signature
 		local symbol, parameters

anselme/parser/expression/primary/symbol.lua

@@ -8,18 +8,17 @@ local Nil = ast.Nil
 
 return primary {
 	match = function(self, str)
-		if str:match("^%::?&?@?") then
+		if str:match("^%:&?@?") then
 			return identifier:match(str:match("^%::?&?@?(.-)$"))
 		end
 		return false
 	end,
 
 	parse = function(self, source, options, str)
-		local mod_const, mod_alias, mod_export, rem = source:consume(str:match("^(%:(:?)(&?)(@?))(.-)$"))
-		local constant, alias, value_check_exp, exported
+		local mod_alias, mod_export, rem = source:consume(str:match("^(%:(&?)(@?))(.-)$"))
+		local alias, value_check_exp, exported
 
 		-- get modifier
-		if mod_const == ":" then constant = true end
 		if mod_alias == "&" then alias = true end
 		if mod_export == "@" then exported = true end
 
@@ -35,6 +34,6 @@ return primary {
 			value_check_exp = exp.arguments.positional[2]
 		end
 
-		return ident:to_symbol{ constant = constant, alias = alias, exported = exported, value_check = value_check_exp }:set_source(source), rem
+		return ident:to_symbol{ alias = alias, exported = exported, value_check = value_check_exp }:set_source(source), rem
 	end
 }

anselme/state/ScopeStack.lua

@@ -47,7 +47,7 @@ local ScopeStack = class {
 	-- for lua functions: define_lua("name", "(x, y, z=5)", function(x, y, z) ... end), where arguments and return values of the function are automatically converted between anselme and lua values
 	-- for other lua values: define_lua("name", value)
 	-- for anselme AST: define_lua("name", value)
-	-- name can be prefixed with symbol modifiers, for example ":name" for a constant variable
+	-- name can be prefixed with symbol modifiers, for example "@name" for an exported variable
 	-- if `raw_mode` is true, no anselme-to/from-lua conversion will be performed in the function
 	-- the function will receive the state followed by AST nodes as arguments, and is expected to return an AST node
 	define_lua = function(self, name, value, func, raw_mode)

anselme/state/State.lua

@@ -104,7 +104,7 @@ State = class {
 	-- * for other lua values: `define("name", value)`
 	-- * for anselme AST: `define("name", value)`
 	--
-	-- `name` can be prefixed with symbol modifiers, for example ":name" for a constant variable.
+	-- `name` can be prefixed with symbol modifiers, for example "@name" for an exported variable.
 	--
 	-- If `raw_mode` is true, no anselme-to/from-lua conversion will be performed in the function.
 	-- The function will receive the state followed by AST nodes as arguments, and is expected to return an AST node.

anselme/stdlib/assignment.lua

@@ -2,6 +2,13 @@ local ast = require("anselme.ast")
 local Nil, Boolean, LuaCall, ParameterTuple, FunctionParameter, Identifier, Overloadable, Overload, Call, Quote = ast.Nil, ast.Boolean, ast.LuaCall, ast.ParameterTuple, ast.FunctionParameter, ast.Identifier, ast.abstract.Overloadable, ast.Overload, ast.Call, ast.Quote
 
 return {
+	{
+		"constant", "(exp)",
+		function(state, exp)
+			return Boolean:new(false)
+		end
+	},
+
 	{
 		"is tuple", "(exp)",
 		function(state, exp)

doc/api.md

@@ -172,7 +172,7 @@ Define a value in the global scope, converting it from Lua to Anselme if needed.
 * for other lua values: `define("name", value)`
 * for anselme AST: `define("name", value)`
 
-`name` can be prefixed with symbol modifiers, for example ":name" for a constant variable.
+`name` can be prefixed with symbol modifiers, for example "@name" for an exported variable.
 
 If `raw_mode` is true, no anselme-to/from-lua conversion will be performed in the function.
 The function will receive the state followed by AST nodes as arguments, and is expected to return an AST node.

test/results/constant variable.ans

@@ -1,7 +1,7 @@
 --# run #--
 --- error ---
-trying to change the value of constant a
+can not set a = 52; constant value check failed
 	↳ from test/tests/constant variable.ans:5:3 in call: a = 52
-	↳ from test/tests/constant variable.ans:1:1 in block: ::a = 3…
+	↳ from test/tests/constant variable.ans:1:1 in block: :a::constant = 3…
 --# saved #--
 {}

test/results/constrained variable assignement.ans

@@ -4,7 +4,7 @@
 --- text ---
 | {}"" {}"type(12, \"kg\")" {}"" |
 --- error ---
-value check failure for weigh; 32 does not satisfy $(x) type(x) == t
+can not set weigh = 32; $(x) type(x) == t value check failed
 	↳ from test/tests/constrained variable assignement.ans:9:7 in call: weigh = 32
 	↳ from test/tests/constrained variable assignement.ans:1:1 in block: :weigh::is("kg") = type(5, "kg")…
 --# saved #--

test/results/symbol alias constant.ans

@@ -5,7 +5,7 @@
 --- text ---
 | {}"d=" {}"2" {}" (2)" |
 --- error ---
-trying to change the value of constant d
+can not set d = 5; constant value check failed
 	↳ from test/tests/symbol alias constant.ans:12:3 in call: d = 5
 	↳ from test/tests/symbol alias constant.ans:1:1 in block: :l = *[1, 2, 3]…
 --# saved #--

test/tests/constant variable list.ans

@@ -1,4 +1,4 @@
-::a = *[3]
+:a::constant = *[3]
 
 |{a}
 

test/tests/constant variable.ans

@@ -1,4 +1,4 @@
-::a = 3
+:a::constant = 3
 
 {a}
 

test/tests/equality operator.ans

@@ -1,4 +1,4 @@
-::a = [1:2]
+:a::constant = [1:2]
 
 |false = {a == [5:2]}
 
@@ -6,7 +6,7 @@
 
 |true = {a == [1:2]}
 
-::b = [1,2,3]
+:b::constant = [1,2,3]
 
 |false = {b == a}
 
@@ -24,6 +24,6 @@
 
 |true = {c!to tuple == b}
 
-::d = [1,2,3]
+:d::constant = [1,2,3]
 
 |true = {d == b}

test/tests/symbol alias constant.ans

@@ -1,11 +1,11 @@
 :l = *[1,2,3]
 
-::&c => l(2)
+:&c::constant => l(2)
 
 | c={c} (2)
 | l={l} (*[1,2,3])
 
-::&d = "{l(2)}"
+:&d::constant = "{l(2)}"
 
 | d={c} (2)