Paste: records as a library

static Bool = NewBoolType();
static Int = NewIntType();
static Pointer[T] = NewPointerType(T);
static Array[T,n] = NewArrayType(T, n);
static Tuple[...T] = NewStructType(...T);


//
// RecordType
//

static RecordType[ID,F] = NewStructType(...FieldTypes(...F));

FieldTypes(first, ...rest) = (FieldType(...first), ...FieldTypes(...rest));
overload FieldTypes() = ();

FieldType(name, type) = type;


//
// Record
//

private var recordId = 1;

private nextRecordId() {
    var x = recordId;
    recordId += 1;
    return x;
}

Record(fields) = RecordType[nextRecordId(), fields];

Record?(x) = false;

[ID,F]
overload Record?(static RecordType[ID,F]) = true;

[ID, F]
RecordFields(static RecordType[ID,F]) = F;


//
// fieldRef
//

procedure fieldRef;

[T | Record?(T)]
overload fieldRef(x:T, ident) {
    static F = RecordFields(T);
    return ref structRef(x, static FieldIndex(ident, static 0, ...F));
}


FieldIndex(ident, i, first, ...rest) {
    var name, type == first;
    if (name == ident)
        return i;
    return FieldIndex(ident, static i+1, ...rest);
}

overload FieldIndex(ident, i) {
    error("field not found");
}


//
// Node[T]
//

static Node[T] = Record((#value, T), (#next, Pointer[Node[T]]));