diff --git a/anselme/stdlib/attached block.lua b/anselme/stdlib/attached block.lua
index 73cbc12..de13040 100644
--- a/anselme/stdlib/attached block.lua	
+++ b/anselme/stdlib/attached block.lua	
@@ -7,7 +7,7 @@ local block_identifier = Identifier:new("_")
 
 return {
 	{
-		"attached block", "(level::number=1, keep return=false)",
+		"attached block", "(level::is number=1, keep return=false)",
 		function(state, level, keep_return)
 			-- level 2: env of the function that called the function that called attached block
 			local env = calling_environment_manager:get_level(state, level:to_lua(state)+1)
@@ -25,7 +25,7 @@ return {
 		end
 	},
 	{
-		"attached block", "(level::number=1, keep return=false, default)",
+		"attached block", "(level::is number=1, keep return=false, default)",
 		function(state, level, keep_return, default)
 			-- level 2: env of the function that called the function that called attached block
 			local env = calling_environment_manager:get_level(state, level:to_lua(state)+1)
diff --git a/anselme/stdlib/boot.lua b/anselme/stdlib/boot.lua
deleted file mode 100644
index a771ad1..0000000
--- a/anselme/stdlib/boot.lua
+++ /dev/null
@@ -1,4 +0,0 @@
-return [[
-:@$is(t) $(x) x!type == t
-:@$equal(x) $(y) x == y
-]]
\ No newline at end of file
diff --git a/anselme/stdlib/for.lua b/anselme/stdlib/for.lua
index bd782fc..e21ed96 100644
--- a/anselme/stdlib/for.lua
+++ b/anselme/stdlib/for.lua
@@ -1,6 +1,6 @@
 return [[
 /* For loop */
-:@$for(symbol::symbol, var, block=attached block(keep return=true))
+:@$for(symbol::is symbol, var, block=attached block(keep return=true))
 	:iterator = iter(var)
 	:value = iterator()
 	:name = symbol!to string
@@ -12,11 +12,12 @@ return [[
 		r
 
 /* Range iterables */
+:@is range = is("range")
 :@$range(stop)
 	[1, stop, 1]!type("range")
 :@$range(start, stop, step=1)
 	[start, stop, step]!type("range")
-:@$iter(range::is("range"))
+:@$iter(range::is range)
 	:v = range!value
 	:start = v(1)
 	:stop = v(2)
@@ -34,8 +35,7 @@ return [[
 				return(i-step)
 
 /* List/tuple iterables */
-:tuple or list = $(x) x!type == "tuple" | x!type == "list"
-:@$iter(tuple::tuple or list)
+:@$iter(tuple::is sequence)
 	:n = tuple!len
 	:i = 0
 	$
@@ -44,7 +44,7 @@ return [[
 			return(tuple(i))
 
 /* Table */
-:@$iter(table::table)
+:@$iter(table::is table)
 	:s = table!to struct
 	iter(s)
 ]]
diff --git a/anselme/stdlib/function.lua b/anselme/stdlib/function.lua
index 6ad0633..a8c9158 100644
--- a/anselme/stdlib/function.lua
+++ b/anselme/stdlib/function.lua
@@ -4,13 +4,13 @@ local assert0 = require("anselme.common").assert0
 
 return {
 	{
-		"defined", "(c::function, s::string)",
+		"defined", "(c::is function, s::is string)",
 		function(state, c, s)
 			return Boolean:new(c.scope:defined_in_current(state, s:to_identifier()))
 		end
 	},
 	{
-		"has upvalue", "(c::function, s::string)",
+		"has upvalue", "(c::is function, s::is string)",
 		function(state, c, s)
 			return Boolean:new(c.scope:defined(state, s:to_identifier()))
 		end
@@ -25,7 +25,7 @@ return {
 		end
 	},
 	{
-		"_._", "(c::function, s::string) = v",
+		"_._", "(c::is function, s::is string) = v",
 		function(state, c, s, v)
 			local identifier = s:to_identifier()
 			assert0(c.scope:defined(state, identifier), ("no variable %q defined in closure"):format(s.string))
@@ -34,7 +34,7 @@ return {
 		end
 	},
 	{
-		"_._", "(c::function, s::symbol) = v",
+		"_._", "(c::is function, s::is symbol) = v",
 		function(state, c, s, v)
 			state.scope:push(c.scope)
 			local r = Definition:new(s, v):eval(state)
diff --git a/anselme/stdlib/init.lua b/anselme/stdlib/init.lua
index 0f65395..e4efea6 100644
--- a/anselme/stdlib/init.lua
+++ b/anselme/stdlib/init.lua
@@ -9,7 +9,7 @@ local function load(state, l)
 	for _, m in ipairs(l) do
 		local mod = require("anselme.stdlib."..m)
 		if type(mod) == "string" then
-			parser(mod, m..".ans"):eval(state)
+			parser(mod, "stdlib/"..m..".ans"):eval(state)
 		else
 			define_lua(state, mod)
 		end
@@ -22,8 +22,8 @@ return function(main_state)
 		"tag",
 		"conditionals",
 		"base",
-		"types",
-		"boot",
+		"typed",
+		"type check",
 		"number",
 		"string",
 		"symbol",
diff --git a/anselme/stdlib/number.lua b/anselme/stdlib/number.lua
index d5700ea..3240e39 100644
--- a/anselme/stdlib/number.lua
+++ b/anselme/stdlib/number.lua
@@ -5,58 +5,58 @@ return {
 	{ "pi", Number:new(math.pi) },
 
 	{
-		"_<_", "(a::number, b::number)",
+		"_<_", "(a::is number, b::is number)",
 		function(state, a, b)
 			if a.number < b.number then return b
 			else return Boolean:new(false)
 			end
 		end
 	},
-	{ "_<_", "(a::equal(false), b::number)", function(state, a, b) return Boolean:new(false) end },
+	{ "_<_", "(a::equal(false), b::is number)", function(state, a, b) return Boolean:new(false) end },
 	{
-		"_<=_", "(a::number, b::number)",
+		"_<=_", "(a::is number, b::is number)",
 		function(state, a, b)
 			if a.number <= b.number then return b
 			else return Boolean:new(false)
 			end
 		end
 	},
-	{ "_<=_", "(a::equal(false), b::number)", function(state, a, b) return Boolean:new(false) end },
+	{ "_<=_", "(a::equal(false), b::is number)", function(state, a, b) return Boolean:new(false) end },
 	{
-		"_>_", "(a::number, b::number)",
+		"_>_", "(a::is number, b::is number)",
 		function(state, a, b)
 			if a.number > b.number then return b
 			else return Boolean:new(false)
 			end
 		end
 	},
-	{ "_>_", "(a::equal(false), b::number)", function(state, a, b) return Boolean:new(false) end },
+	{ "_>_", "(a::equal(false), b::is number)", function(state, a, b) return Boolean:new(false) end },
 	{
-		"_>=_", "(a::number, b::number)",
+		"_>=_", "(a::is number, b::is number)",
 		function(state, a, b)
 			if a.number >= b.number then return b
 			else return Boolean:new(false)
 			end
 		end
 	},
-	{ "_>=_", "(a::equal(false), b::number)", function(state, a, b) return Boolean:new(false) end },
-	{ "_+_", "(a::number, b::number)", function(state, a, b) return Number:new(a.number + b.number) end },
-	{ "_-_", "(a::number, b::number)", function(state, a, b) return Number:new(a.number - b.number) end },
-	{ "_*_", "(a::number, b::number)", function(state, a, b) return Number:new(a.number * b.number) end },
-	{ "_/_", "(a::number, b::number)", function(state, a, b) return Number:new(a.number / b.number) end },
-	{ "_//_", "(a::number, b::number)", function(state, a, b) return Number:new(math.floor(a.number / b.number)) end },
-	{ "_%_", "(a::number, b::number)", function(state, a, b) return Number:new(a.number % b.number) end },
-	{ "_^_", "(a::number, b::number)", function(state, a, b) return Number:new(a.number ^ b.number) end },
-	{ "-_", "(a::number)", function(state, a) return Number:new(-a.number) end },
+	{ "_>=_", "(a::equal(false), b::is number)", function(state, a, b) return Boolean:new(false) end },
+	{ "_+_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number + b.number) end },
+	{ "_-_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number - b.number) end },
+	{ "_*_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number * b.number) end },
+	{ "_/_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number / b.number) end },
+	{ "_//_", "(a::is number, b::is number)", function(state, a, b) return Number:new(math.floor(a.number / b.number)) end },
+	{ "_%_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number % b.number) end },
+	{ "_^_", "(a::is number, b::is number)", function(state, a, b) return Number:new(a.number ^ b.number) end },
+	{ "-_", "(a::is number)", function(state, a) return Number:new(-a.number) end },
 
-	{ "rand", "(min::number, max::number)", function(state, min, max) return Number:new(math.random(min.number, max.number)) end },
-	{ "rand", "(max::number)", function(state, max) return Number:new(math.random(max.number)) end },
+	{ "rand", "(min::is number, max::is number)", function(state, min, max) return Number:new(math.random(min.number, max.number)) end },
+	{ "rand", "(max::is number)", function(state, max) return Number:new(math.random(max.number)) end },
 	{ "rand", "()", function(state) return Number:new(math.random()) end },
 
-	{ "floor", "(x::number)", function(state, x) return Number:new(math.floor(x.number)) end },
-	{ "ceil", "(x::number)", function(state, x) return Number:new(math.ceil(x.number)) end },
+	{ "floor", "(x::is number)", function(state, x) return Number:new(math.floor(x.number)) end },
+	{ "ceil", "(x::is number)", function(state, x) return Number:new(math.ceil(x.number)) end },
 	{
-		"round", "(x::number, increment=1)",
+		"round", "(x::is number, increment=1)",
 		function(state, x, increment)
 			local n = x.number / increment.number
 			if n >= 0 then
diff --git a/anselme/stdlib/pair.lua b/anselme/stdlib/pair.lua
index 71ee328..fe55c4a 100644
--- a/anselme/stdlib/pair.lua
+++ b/anselme/stdlib/pair.lua
@@ -5,13 +5,13 @@ return {
 	{ "_:_", "(name, value)", function(state, a, b) return Pair:new(a,b) end },
 
 	{
-		"name", "(pair::pair)",
+		"name", "(pair::is pair)",
 		function(state, pair)
 			return pair.name
 		end
 	},
 	{
-		"value", "(pair::pair)",
+		"value", "(pair::is pair)",
 		function(state, pair)
 			return pair.value
 		end
diff --git a/anselme/stdlib/resume.lua b/anselme/stdlib/resume.lua
index fd74218..3710b9b 100644
--- a/anselme/stdlib/resume.lua
+++ b/anselme/stdlib/resume.lua
@@ -6,13 +6,13 @@ local calling_environment_manager = require("anselme.state.calling_environment_m
 
 return {
 	{
-		"from", "(function::function, anchor::anchor)",
+		"from", "(function::is function, anchor::is anchor)",
 		function(state, func, anchor)
 			return func:resume(state, anchor)
 		end
 	},
 	{
-		"from", "(function::function, anchor::nil)",
+		"from", "(function::is function, anchor::is nil)",
 		function(state, func)
 			return func:call(state, ArgumentTuple:new())
 		end
@@ -24,7 +24,7 @@ return {
 		end
 	},
 	{
-		"resuming", "(level::number=0)",
+		"resuming", "(level::is number=0)",
 		function(state, level)
 			local env = calling_environment_manager:get_level(state, level:to_lua(state)+1)
 			state.scope:push(env)
diff --git a/anselme/stdlib/script.lua b/anselme/stdlib/script.lua
index 8d2a76d..6b7d033 100644
--- a/anselme/stdlib/script.lua
+++ b/anselme/stdlib/script.lua
@@ -6,9 +6,9 @@ return [[
 
 	:resume target = ()
 
-	fn.:check = $(anchor::anchor)
+	fn.:check = $(anchor::is anchor)
 		fn.reached(anchor) = (fn.reached(anchor) | 0) + 1
-	fn.:checkpoint = $(anchor::anchor, on resume=attached block(default=()))
+	fn.:checkpoint = $(anchor::is anchor, on resume=attached block(default=()))
 		if(on resume)
 			fn.current checkpoint = anchor
 			if(resume target == anchor | resuming(4))
@@ -38,14 +38,14 @@ return [[
 :@$_!(s::is script)
 	s!value!
 
-:@$_._(s::is script, k::string)
+:@$_._(s::is script, k::is string)
 	(s!value).fn.(k)
-:@$_._(s::is script, k::string) = val
+:@$_._(s::is script, k::is string) = val
 	(s!value).fn.(k) = val
-:@$_._(s::is script, k::symbol) = val
+:@$_._(s::is script, k::is symbol) = val
 	(s!value).fn.(k) = val
 
-:@$from(s::is script, a::anchor)
+:@$from(s::is script, a::is anchor)
 	s.current checkpoint = a
 	return(s!)
 :@$from(s::is script)
@@ -53,7 +53,7 @@ return [[
 	return(s!)
 
 /* Additionnal helpers */
-:@$ cycle(l::tuple)
+:@$ cycle(l::is tuple)
 	:i = 2
 	while($i <= l!len)
 		if(l(i).run < l(1).run)
@@ -61,7 +61,7 @@ return [[
 		i += 1
 	l(1)!
 
-:@$ next(l::tuple)
+:@$ next(l::is tuple)
 	:i = 1
 	while($i <= l!len)
 		if(l(i).run == 0)
@@ -69,6 +69,6 @@ return [[
 		i += 1
 	l(i-1)!
 
-:@$ random(l::tuple)
+:@$ random(l::is tuple)
 	l(rand(1, l!len))!
 ]]
\ No newline at end of file
diff --git a/anselme/stdlib/string.lua b/anselme/stdlib/string.lua
index b1ddb06..f89d6b0 100644
--- a/anselme/stdlib/string.lua
+++ b/anselme/stdlib/string.lua
@@ -3,9 +3,9 @@ local ast = require("anselme.ast")
 local String, Number = ast.String, ast.Number
 
 return {
-	{ "_+_", "(a::string, b::string)", function(state, a, b) return String:new(a.string .. b.string) end },
+	{ "_+_", "(a::is string, b::is string)", function(state, a, b) return String:new(a.string .. b.string) end },
 	{
-		"len", "(s::string)",
+		"len", "(s::is string)",
 		function(state, s)
 			return Number:new(utf8.len(s.string))
 		end
diff --git a/anselme/stdlib/structures.lua b/anselme/stdlib/structures.lua
index a104d1b..4aa0776 100644
--- a/anselme/stdlib/structures.lua
+++ b/anselme/stdlib/structures.lua
@@ -4,25 +4,25 @@ local Nil, List, Table, Number, LuaFunction, ParameterTuple, Boolean = ast.Nil,
 return {
 	-- tuple
 	{
-		"*_", "(t::tuple)",
+		"*_", "(t::is tuple)",
 		function(state, tuple)
 			return List:new(state, tuple)
 		end
 	},
 	{
-		"_!", "(l::tuple, i::number)",
+		"_!", "(l::is tuple, i::is number)",
 		function(state, l, i)
 			return l:get(i.number)
 		end
 	},
 	{
-		"len", "(l::tuple)",
+		"len", "(l::is tuple)",
 		function(state, l)
 			return Number:new(l:len())
 		end
 	},
 	{
-		"find", "(l::tuple, value)",
+		"find", "(l::is tuple, value)",
 		function(state, l, v)
 			local i = l:find(v)
 			if i then
@@ -35,26 +35,26 @@ return {
 
 	-- list
 	{
-		"_!", "(l::list, i::number)",
+		"_!", "(l::is list, i::is number)",
 		function(state, l, i)
 			return l:get(state, i.number)
 		end
 	},
 	{
-		"_!", "(l::list, i::number) = value",
+		"_!", "(l::is list, i::is number) = value",
 		function(state, l, i, v)
 			l:set(state, i.number, v)
 			return Nil:new()
 		end
 	},
 	{
-		"len", "(l::list)",
+		"len", "(l::is list)",
 		function(state, l)
 			return Number:new(l:len(state))
 		end
 	},
 	{
-		"find", "(l::list, value)",
+		"find", "(l::is list, value)",
 		function(state, l, v)
 			local i = l:find(state, v)
 			if i then
@@ -65,35 +65,35 @@ return {
 		end
 	},
 	{
-		"insert", "(l::list, value)",
+		"insert", "(l::is list, value)",
 		function(state, l, v)
 			l:insert(state, v)
 			return Nil:new()
 		end
 	},
 	{
-		"insert", "(l::list, position::number, value)",
+		"insert", "(l::is list, position::is number, value)",
 		function(state, l, position, v)
 			l:insert(state, position.number, v)
 			return Nil:new()
 		end
 	},
 	{
-		"remove", "(l::list)",
+		"remove", "(l::is list)",
 		function(state, l)
 			l:remove(state)
 			return Nil:new()
 		end
 	},
 	{
-		"remove", "(l::list, position::number)",
+		"remove", "(l::is list, position::is number)",
 		function(state, l, position)
 			l:remove(state, position.number)
 			return Nil:new()
 		end
 	},
 	{
-		"to tuple", "(l::list)",
+		"to tuple", "(l::is list)",
 		function(state, l)
 			return l:to_tuple(state)
 		end
@@ -101,25 +101,25 @@ return {
 
 	-- struct
 	{
-		"*_", "(s::struct)",
+		"*_", "(s::is struct)",
 		function(state, struct)
 			return Table:new(state, struct)
 		end
 	},
 	{
-		"_!", "(s::struct, key)",
+		"_!", "(s::is struct, key)",
 		function(state, s, k)
 			return s:get(k)
 		end
 	},
 	{
-		"has", "(s::struct, key)",
+		"has", "(s::is struct, key)",
 		function(state, s, k)
 			return Boolean:new(s:has(k))
 		end
 	},
 	{
-		"iter", "(s::struct)",
+		"iter", "(s::is struct)",
 		function(state, struct)
 			local iter = struct:iter()
 			return LuaFunction:new(ParameterTuple:new(), function()
@@ -132,26 +132,26 @@ return {
 
 	-- table
 	{
-		"_!", "(t::table, key)",
+		"_!", "(t::is table, key)",
 		function(state, t, key)
 			return t:get(state, key)
 		end
 	},
 	{
-		"_!", "(t::table, key) = value",
+		"_!", "(t::is table, key) = value",
 		function(state, t, key, value)
 		t:set(state, key, value)
 			return Nil:new()
 		end
 	},
 	{
-		"has", "(t::table, key)",
+		"has", "(t::is table, key)",
 		function(state, t, k)
 			return Boolean:new(t:has(state, k))
 		end
 	},
 	{
-		"to struct", "(t::table)",
+		"to struct", "(t::is table)",
 		function(state, t)
 			return t:to_struct(state)
 		end
diff --git a/anselme/stdlib/symbol.lua b/anselme/stdlib/symbol.lua
index e5e22dd..defef4c 100644
--- a/anselme/stdlib/symbol.lua
+++ b/anselme/stdlib/symbol.lua
@@ -1,7 +1,7 @@
 return {
 
 	{
-		"to string", "(symbol::symbol)",
+		"to string", "(symbol::is symbol)",
 		function(state, sym)
 			return sym:to_string()
 		end
diff --git a/anselme/stdlib/text.lua b/anselme/stdlib/text.lua
index 2c97f0a..f24599f 100644
--- a/anselme/stdlib/text.lua
+++ b/anselme/stdlib/text.lua
@@ -9,7 +9,7 @@ local resume_manager = require("anselme.state.resume_manager")
 return {
 	-- text
 	{
-		"_+_", "(a::text, b::text)",
+		"_+_", "(a::is text, b::is text)",
 		function(state, a, b)
 			local r = Text:new()
 			for _, e in ipairs(a.list) do
@@ -22,7 +22,7 @@ return {
 		end
 	},
 	{
-		"_!", "(txt::text)",
+		"_!", "(txt::is text)",
 		function(state, text)
 			event_manager:write(state, text)
 			return Nil:new()
@@ -31,7 +31,7 @@ return {
 
 	-- choice
 	{
-		"_|>_", "(txt::text, fn)",
+		"_|>_", "(txt::is text, fn)",
 		function(state, text, func)
 			if func:contains_current_resume_target(state) then
 				func:call(state, ArgumentTuple:new())
diff --git a/anselme/stdlib/type check.lua b/anselme/stdlib/type check.lua
new file mode 100644
index 0000000..e0da8a0
--- /dev/null
+++ b/anselme/stdlib/type check.lua	
@@ -0,0 +1,26 @@
+return [[
+:@$is(t) $(x) x!type == t
+:@$equal(x) $(y) x == y
+
+:@is nil = is("nil")
+:@is number = is("number")
+:@is string = is("string")
+:@is boolean = is("boolean")
+:@is symbol = is("symbol")
+:@is anchor = is("anchor")
+:@is pair = is("pair")
+
+:@is text = is("text")
+
+:@is sequence = $(x) x!type == "tuple" | x!type == "list"
+:@is tuple = is("tuple")
+:@is list = is("list")
+
+:@is map = $(x) x!type == "struct" | x!type == "table"
+:@is struct = is("struct")
+:@is table = is("table")
+
+:@is function = is("function")
+:@is overload = is("overload")
+:@is callable = $(x) x!type == "overload" | x!type == "function" | x!type == "lua function" | x!type == "quote"
+]]
\ No newline at end of file
diff --git a/anselme/stdlib/typed.lua b/anselme/stdlib/typed.lua
new file mode 100644
index 0000000..999e7da
--- /dev/null
+++ b/anselme/stdlib/typed.lua
@@ -0,0 +1,43 @@
+local ast = require("anselme.ast")
+local ArgumentTuple, String, Typed = ast.ArgumentTuple, ast.String, ast.Typed
+
+return {
+	{
+		"_::_", "(value, check)",
+		function(state, value, check)
+			local r = check:call(state, ArgumentTuple:new(value))
+			if r:truthy() then
+				return value
+			else
+				error(("type check failure: %s does not satisfy %s"):format(value:format(state), check:format(state)), 0)
+			end
+		end
+	},
+
+	{
+		"type", "(value)",
+		function(state, v)
+			if v.type == "typed" then
+				return v.type_expression
+			else
+				return String:new(v.type)
+			end
+		end
+	},
+	{
+		"type", "(value, type)",
+		function(state, v, t)
+			return Typed:new(v, t)
+		end
+	},
+	{
+		"value", "(value)",
+		function(state, v)
+			if v.type == "typed" then
+				return v.expression
+			else
+				return v
+			end
+		end
+	},
+}
diff --git a/anselme/stdlib/types.lua b/anselme/stdlib/types.lua
deleted file mode 100644
index 660dd69..0000000
--- a/anselme/stdlib/types.lua
+++ /dev/null
@@ -1,62 +0,0 @@
-local ast = require("anselme.ast")
-local ArgumentTuple, Boolean, String, Typed = ast.ArgumentTuple, ast.Boolean, ast.String, ast.Typed
-
-return {
-	{
-		"_::_", "(value, check)",
-		function(state, value, check)
-			local r = check:call(state, ArgumentTuple:new(value))
-			if r:truthy() then
-				return value
-			else
-				error(("type check failure: %s does not satisfy %s"):format(value:format(state), check:format(state)), 0)
-			end
-		end
-	},
-
-	{
-		"type", "(value)",
-		function(state, v)
-			if v.type == "typed" then
-				return v.type_expression
-			else
-				return String:new(v.type)
-			end
-		end
-	},
-	{
-		"type", "(value, type)",
-		function(state, v, t)
-			return Typed:new(v, t)
-		end
-	},
-	{
-		"value", "(value)",
-		function(state, v)
-			if v.type == "typed" then
-				return v.expression
-			else
-				return v
-			end
-		end
-	},
-
-	{ "nil", "(x)", function(state, x) return Boolean:new(x.type == "nil") end },
-	{ "number", "(x)", function(state, x) return Boolean:new(x.type == "number") end },
-	{ "string", "(x)", function(state, x) return Boolean:new(x.type == "string") end },
-	{ "boolean", "(x)", function(state, x) return Boolean:new(x.type == "boolean") end },
-	{ "symbol", "(x)", function(state, x) return Boolean:new(x.type == "symbol") end },
-	{ "anchor", "(x)", function(state, x) return Boolean:new(x.type == "anchor") end },
-
-	{ "text", "(x)", function(state, x) return Boolean:new(x.type == "text") end },
-
-	{ "pair", "(x)", function(state, x) return Boolean:new(x.type == "pair") end },
-	{ "tuple", "(x)", function(state, x) return Boolean:new(x.type == "tuple") end },
-	{ "list", "(x)", function(state, x) return Boolean:new(x.type == "list") end },
-	{ "struct", "(x)", function(state, x) return Boolean:new(x.type == "struct") end },
-	{ "table", "(x)", function(state, x) return Boolean:new(x.type == "table") end },
-
-	{ "function", "(x)", function(state, x) return Boolean:new(x.type == "function") end },
-	{ "overload", "(x)", function(state, x) return Boolean:new(x.type == "overload") end },
-	{ "callable", "(x)", function(state, x) return Boolean:new(x.type == "overload" or x.type == "function" or x.type == "lua function" or x.type == "quote") end },
-}
diff --git a/test/run.lua b/test/run.lua
index a9a3b9e..61cab2c 100644
--- a/test/run.lua
+++ b/test/run.lua
@@ -76,9 +76,9 @@ local function run(path, interactive)
 	local state = anselme:new()
 	state:load_stdlib()
 
-	state:define("interrupt", "(code::string)", function(state, code) state:interrupt(code:to_lua(state), "interrupt") return ast.Nil:new() end, true)
+	state:define("interrupt", "(code::is string)", function(state, code) state:interrupt(code:to_lua(state), "interrupt") return ast.Nil:new() end, true)
 	state:define("interrupt", "()", function(state) state:interrupt() return ast.Nil:new() end, true)
-	state:define("wait", "(duration::number)", function(duration) coroutine.yield("wait", duration) end)
+	state:define("wait", "(duration::is number)", function(duration) coroutine.yield("wait", duration) end)
 	state:define("run in new branch", "(code)", function(code)
 		local parallel_state = state:branch()
 		write_output("--# parallel script #--")
@@ -87,7 +87,7 @@ local function run(path, interactive)
 		write_output("--# main script #--")
 	end)
 	state:define("serialize", "(value)", function(state, value) return ast.String:new(value:serialize(state)) end, true)
-	state:define("deserialize", "(str::string)", function(state, str) return ast.abstract.Node:deserialize(state, str.string) end, true)
+	state:define("deserialize", "(str::is string)", function(state, str) return ast.abstract.Node:deserialize(state, str.string) end, true)
 
 	local run_state = state:branch()
 
@@ -123,7 +123,7 @@ end
 if not arg[1] or arg[1] == "update" then
 	-- display an animated loading indicator
 	local loading = {
-		loop = { "⣾", "⣽", "⣻", "⢿", "⡿", "⣟", "⣯", "⣷" },
+		loop = { "⣷", "⣯", "⣟", "⡿", "⢿", "⣻", "⣽", "⣾" },
 		loop_pos = 1,
 		erase_code = "",
 
diff --git a/test/tests/binary operator overload.ans b/test/tests/binary operator overload.ans
index bc811a9..5b48809 100644
--- a/test/tests/binary operator overload.ans	
+++ b/test/tests/binary operator overload.ans	
@@ -1,7 +1,7 @@
 :$ a - b
 	return("generic minus")
 
-:$ a::string - b::string
+:$ a::is string - b::is string
 	return(a + " minus " + b)
 
 | {2-5}
diff --git a/test/tests/function assignement.ans b/test/tests/function assignement.ans
index 321ebca..a142856 100644
--- a/test/tests/function assignement.ans	
+++ b/test/tests/function assignement.ans	
@@ -7,7 +7,7 @@
 	|v={v}
 	a = v
 
-:$ f(p) = v::string
+:$ f(p) = v::is string
 	|v2={v}
 	a = p
 
diff --git a/test/tests/function selection.ans b/test/tests/function selection.ans
index cd2ecb1..4da0aa8 100644
--- a/test/tests/function selection.ans	
+++ b/test/tests/function selection.ans	
@@ -1,8 +1,8 @@
-:$ a(x::number)
+:$ a(x::is number)
 	return(x + 2)
 
 :$ x
-	:$ a(x::string)
+	:$ a(x::is string)
 		return(x + "heh")
 
 	|{a("plop")}
diff --git a/test/tests/function type dispatch ambigous.ans b/test/tests/function type dispatch ambigous.ans
index 6c65d14..0b07fd9 100644
--- a/test/tests/function type dispatch ambigous.ans	
+++ b/test/tests/function type dispatch ambigous.ans	
@@ -1,7 +1,7 @@
-:$ fn(x::number)
+:$ fn(x::is number)
 	|x
 
-:$ fn(a::number)
+:$ fn(a::is number)
 	|a
 
 fn(5)
diff --git a/test/tests/function type dispatch with default.ans b/test/tests/function type dispatch with default.ans
index 3cca2c4..5e04116 100644
--- a/test/tests/function type dispatch with default.ans	
+++ b/test/tests/function type dispatch with default.ans	
@@ -1,7 +1,7 @@
-:$ fn(x::number)
+:$ fn(x::is number)
 	|x
 
-:$ fn(a::string="o")
+:$ fn(a::is string="o")
 	|a
 
 fn("s")
@@ -10,10 +10,10 @@ fn(5)
 
 fn()
 
-:$ g(n="s", a::number=5)
+:$ g(n="s", a::is number=5)
 	return("gn")
 
-:$ g(n="s", a::string="lol")
+:$ g(n="s", a::is string="lol")
 	return("gs")
 
 |{g(n="k", a="l")}
diff --git a/test/tests/function type dispatch.ans b/test/tests/function type dispatch.ans
index ead73d8..77c6d5a 100644
--- a/test/tests/function type dispatch.ans	
+++ b/test/tests/function type dispatch.ans	
@@ -1,7 +1,7 @@
-:$ fn(x::number)
+:$ fn(x::is number)
 	|x
 
-:$ fn(a::string)
+:$ fn(a::is string)
 	|a
 
 fn("s")
diff --git a/test/tests/serialize function.ans b/test/tests/serialize function.ans
index b009d40..a7060e8 100644
--- a/test/tests/serialize function.ans	
+++ b/test/tests/serialize function.ans	
@@ -1,6 +1,6 @@
 :f = ()
 _
-	:$_+_(a::string, b)
+	:$_+_(a::is string, b)
 		"{a}{b}"
 
 	:a=1
diff --git a/test/tests/unary operator overload.ans b/test/tests/unary operator overload.ans
index 7f97052..b6aec57 100644
--- a/test/tests/unary operator overload.ans	
+++ b/test/tests/unary operator overload.ans	
@@ -1,7 +1,7 @@
 :$ -f
 	return("generic minus")
 
-:$ -f::string
+:$ -f::is string
 	return("minus "+f)
 
 |{-5}