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i try to use the code:

#lang at-exp racket
(require infix)
(define txt "2+2")
@${ txt } or ($ "txt")

but the output it's the string "2+2" and not the evaluation @${2+2} or ($ "2+2") -> 4
it is posible to use a string as argument of $ to be evaluated as i need?

If I have this program in DrRacket:

#lang at-exp racket
(require infix)
(let ([a '(1 1)] [b '(2 3)] [+ (λ (a b) (map + a b))])
  @${a+b})

And then I right-click on the a in @${a+b} then the check-syntax arrow points the the right thing, but the menu pops up with an option saying rename +, then if I proceed to rename it to, say -, then it changes it to:

(let ([- '(1 1)] [b '(2 3)] [- (λ (a b) (map + a b))])
  @${--b})

In other words, it renames both a and + to -.
Do you have any idea what could be causing this?

In programs like this:

#lang at-exp racket/base
(require infix)
(define x0 0)
(define v 5)
(define dt 1)
@${x@"0" + v*dt}

Because direct string escapes are handled specially by the at-exp reader, this expands directly to ($ "x0 + v*dt"), so it thinks the v and the dt are 3 characters before where they are.