help with Wrong type of argument

[Jeff Olson]

I'm starting to translate some of my \postscript markups into lilypond 
in order to use cairo, and it seems I always stub my toe when trying to 
use a variable in a substitution function.

In this example I'm trying to do (lineto 0 hgt) which fails with "In 
procedure *: Wrong type argument in position 1: hgt".

But it works if I replace hgt with a constant: (lineto 0 2).

My cargo cult thinking was that this lineto command was in a scheme 
expression so I shouldn't use a # or $ before the hgt variable to 
reference it (like the xtip and ytip inside the cons).

I'd welcome a quick syntax fix or a reference to what I should have read 
before asking.

TIA,
Jeff

Here's my code (small if not minimal):

\version "2.24.0"

#(define-markup-command (dopath layout props xtip ytip hgt wid txt rot)
  (number? number? number? number? string? number?)
  (let (
         (a (* wid 0.4))
         )
  (interpret-markup layout props
    #{\markup \translate #(cons xtip ytip) \rotate #rot \path #0.25
      #'((lineto 0 hgt)
         (closepath))
      #})))

\markup \dopath #10 #0 #2 #1 "D" #-5