types.js

Type variable

A type variable represents an parameter with an unknown type or any polymorphic type. For example:

fun id x = x

Here, id has the polymorphic type 'a -> 'a.

 
var Variable = function() {
    this.id = Variable.nextId;
    Variable.nextId++;
    this.instance = null;
};
Variable.nextId = 0;
exports.Variable = Variable;

Type variables should look like 'a. If the variable has an instance, that should be used for the string instead.

 
Variable.prototype.toString = function() {
    if(!this.instance) {
	return "'" + String.fromCharCode("a".charCodeAt(0) + this.id);
    }
    return this.instance.toString();
};

Base type

Base type for all specific types. Using this type as the prototype allows the use of instanceof to detect a type variable or an actual type.

 
var BaseType = function(name, types) {
    this.name = name;
    this.types = types;
};
BaseType.prototype.toString = function() {
    var typeString;
    if(this.types.length) {
	typeString = this.types.map(function(type) {
	    return type.toString();
	}).toString();
	return this.name + "(" + typeString + ")";
    }
    return this.name;
};
exports.BaseType = BaseType;

Specific types

A FunctionType contains a types array. The last element represents the return type. Each element before represents an argument type. 

var FunctionType = function(types) {
    this.types = types;
};
FunctionType.prototype = new BaseType("Function");
exports.FunctionType = FunctionType;

var NumberType = function() {};
NumberType.prototype = new BaseType("Number", []);
exports.NumberType = NumberType;

var StringType = function() {};
StringType.prototype = new BaseType("String", []);
exports.StringType = StringType;