Beau­tiful Racket / racket school 2019

• 1 intro
• 2 pl check­list
• 3 lop till you drop
• 4 lop exam­ples
• 5 bullet train
• 6 trigram
• 7 flyover country
• 8 read only
• 9 expand only
• 10 conjunc­tion
• 11 injunc­tion

1. 

   Inter­po­si­tion points are special macros that Racket implic­itly inserts as hooks for providing (or over­riding) certain default behavior. We can recog­nize them by their names, which are prefixed with #%.

2. 

   We already saw #%module-begin, which wraps the body of the module, so this:

   

   (module mod-name expander-mod
      expression ···)

   

   1 2	(module mod-name expander-mod expression ···)

   
   

   Becomes:

   

   (module mod-name expander-mod
      (#%module-begin expression ···))

   

   1 2	(module mod-name expander-mod (#%module-begin expression ···))

   
   

   By providing a #%module-begin macro, we control what happens at this moment in the eval­u­a­tion.

   

   Ques­tion: why not just provide a module macro?

3. 

   Inter­po­si­tion points are exported by the expander. #%module-begin is manda­tory. Others are optional.

4. 

   #%top-interaction: enables the REPL. Does not control how the REPL behaves, about which more here.

5. 

   #lang br/quicklang is a variant of #lang br that exports the default inter­po­si­tion points (except for #%module-begin) so you don’t have to.

test.rkt



#lang conjunction

"hello world"
(+ 1 (* 2 (- x)))



1 2 3 4

#lang conjunction "hello world" (+ 1 (* 2 (- x)))



"whee"
'(kaboom 42 (kaboom 42 (kaboom kaboom)))



1 2	"whee" '(kaboom 42 (kaboom 42 (kaboom kaboom)))

• 1 intro
• 2 pl check­list
• 3 lop till you drop
• 4 lop exam­ples
• 5 bullet train
• 6 trigram
• 7 flyover country
• 8 read only
• 9 expand only
• 10 conjunc­tion
• 11 injunc­tion