Why are there seemingly unnecessary if expressions shown by the Macro stepper?

[schle...@gmail.com]

The [WordCount] thread caused me to play around with the solutions to see whether I could see anything else that can be tweaked, I tried a few things but they didn't improve performance, but it was fun anyway.

Then I though I could try the macro stepper and look at the expansion of [crowdsourced].

I disabled macro hiding and stepped to the end.

There I saw if statements with a condition that is `(quote #t)` with a little lock symbol before it.

I would like to understand why those terms aren't reduced further.

Are they placeholders and are replaced and resolved at a later time?

terms copied (without the lock symbol) from the macro stepper

(if (if '#t (#%app not '#f) '#f)
  (#%app for-loop (#%app unsafe-fx+ '1 pos))
  (#%app values))

From a naive standpoint I would expect it to be simplified:
(if '#t (#%app not '#f) '#f) -> (#%app not '#f)

(if (#%app not '#f)
  (#%app for-loop (#%app unsafe-fx+ '1 pos))
  (#%app values))

So expressed another way: why isn't the if with boolean literal as condition reduced to the corresponding branch? Or does this happen, just isn't shown in the macro stepper?

What am I misunderstanding here?

If there aren't simplifications like that, what is preventing them or making them not worthwhile?

[WordCount] https://groups.google.com/g/racket-users/c/lGA60P6jboY/m/2ZLDAunBBgAJ

[crowdsourced] https://gist.github.com/Bogdanp/b9256e1a91de9083830cb616b3659ff8

[Sorawee Porncharoenwase]

That’s not the job of the macro expander. And the Racket optimizer does reduce (if '#t (#%app not '#f) '#f) — in fact to #t.

If you use Racket CS, try running:

PLT_LINKLET_SHOW_CP0=1 racket file.rkt

where file.rkt is

#lang racket
(displayln (if #t (not #f) #f))

Here’s the optimized program:

;; cp0 ---------------------
(lambda (instance-variable-reference .get-syntax-literal!1
         .set-transformer!2 displayln3 print-values4)
  (call-with-module-prompt
    (lambda ()
      (#%call-with-values
        (lambda () (displayln3 #t))
        print-values4)))
  (#2%void))

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[schle...@gmail.com]

Ahh ok, thank you that makes sense.

I didn't know about PLT_LINKLET_SHOW_CP0 before that is a nice look behind the scene.