1. Goals of my lectures A way of adding types DSL-making “tools”
Another DSL example

2. Goals of my lectures A way of adding types DSL-making “tools”
Another DSL example
Last time:
type-of, type=?, assign-type
define-type
check-type
#%datum
add1
This time:
#%app
lambda
Type constructors
Type checking types

3. Goals of my lectures A way of adding types DSL-making “tools”
Another DSL example
Last time (basic):
syntax-parse
Syntax objects
Syntax properties
Interposition: #%app, #%datum
Today (deep end):
Phasing
Pattern expanders
Id macros
Syntax classes
Definition contexts

4. Goals of my lectures A way of adding types DSL-making “tools”
Another DSL example
Next time

5. Id macros are tricky! Racket macro expansion algorithm:
For syntax object #’(x y z):
If x is macro
Pass #’(x y z) to syntax transformer registered as macro x
Else
Pass #’(#%app x y z) to #%app macro
Ambiguity: what if x = id macro that expands to add1
We want to invoke x macro on just x,
but algorithm doesn’t do that