progress and some refactoring

primitives/symbol.js

@@ -0,0 +1,8 @@
+// The functions are only defined here. For their types, see lib/symbol.js
+
+// The point of having an explicit constructor for SymbolT, is that we can later swap it out for something that is (de-)serializable.
+export const constructSymbol = name => Symbol(name);
+
+export const getName = symbol => symbol.description;
+
+export const eqSymbol = a => b => a === b;

primitives/types.js

@@ -1,9 +1,17 @@
 // to break up dependency cycles, primitive types are defined in their own JS module
 
-export const Int    = { symbol: Symbol('Int')   , params: [] };
-export const Bool   = { symbol: Symbol('Bool')  , params: [] };
-export const Double = { symbol: Symbol('Double'), params: [] };
-export const Byte   = { symbol: Symbol('Byte')  , params: [] };
-export const Char   = { symbol: Symbol('Char')  , params: [] };
+import { makeTypeConstructor } from "../type_constructor.js";
+import { constructSymbol } from "./symbol.js";
 
-export const Type = { symbol: Symbol('Type'), params: [] };
+export const Int     = makeTypeConstructor(constructSymbol('Int'), 0);
+export const Bool    = makeTypeConstructor(constructSymbol('Bool'), 0);
+export const Double  = makeTypeConstructor(constructSymbol('Double'), 0);
+export const Byte    = makeTypeConstructor(constructSymbol('Byte'), 0);
+export const Char    = makeTypeConstructor(constructSymbol('Char'), 0);
+
+// Unit type has only 1 instance, the empty tuple.
+export const Unit    = makeTypeConstructor(constructSymbol('Unit'), 0);
+
+export const SymbolT = makeTypeConstructor(constructSymbol('Symbol'), 0);
+
+export const Type    = makeTypeConstructor(constructSymbol('Type'), 0);

primitives/unit.js

@@ -0,0 +1,13 @@
+import { typedFnType } from "../structures/types.js";
+import { Bool, Type, Unit } from "./types.js";
+
+const eqUnit = x => y => x === y;
+
+export const ModuleUnit = {l:[
+  {i: {}, t: Unit},
+
+  {i: Unit, t: Type},
+
+  // Unit -> Unit -> Bool
+  ...typedFnType(eqUnit, fnType => fnType(Unit)(fnType(Unit)(Bool))),
+]};