Bring Record toward the needs of Syndicate/js Struct

implementations/javascript/src/index.js

@@ -303,6 +303,24 @@ class Record {
     this.fields = fromJS(fields);
   }
 
+  equals(other) {
+    return (other instanceof Record) &&
+      Immutable.is(this.label, other.label) &&
+      Immutable.is(this.fields, other.fields);
+  }
+
+  hashCode() {
+    return Immutable.List([this.label, this.fields]).hashCode();
+  }
+
+  get(index, defaultValue) {
+    return this.fields.get(index, defaultValue);
+  }
+
+  set(index, newValue) {
+    return new Record(this.label, this.fields.set(index, newValue));
+  }
+
   [PreserveOn](encoder) {
     if (Immutable.is(encoder.shortForms[0], this.label)) {
       encoder.header(2, 0, this.fields.size);
@@ -318,11 +336,33 @@ class Record {
   }
 }
 
+Record.makeConstructor = function (label, fieldNames) {
+  const arity = fieldNames.length;
+  const ctor = (...fields) => {
+    if (fields.length !== arity) {
+      throw new Error("Record: cannot instantiate " + (label && label.toString()) +
+                      " expecting " + arity + " fields with " + fields.length + " fields");
+    }
+    return new Record(label, fields);
+  };
+  ctor.meta = label;
+  ctor.isClassOf = (v) => ((v instanceof Record) && Immutable.is(label, v.label));
+  return ctor;
+};
+
 class Float {
   constructor(value) {
     this.value = value;
   }
 
+  equals(other) {
+    return (other instanceof Float) && (other.value === this.value);
+  }
+
+  hashCode() {
+    return this.value | 0; // TODO: something better?
+  }
+
   [PreserveOn](encoder) {
     encoder.leadbyte(0, 0, 2);
     encoder.makeroom(4);