subr.l

Reading this in 2026. This page reproduces doCdr from src64/subr.l from the PicoLisp sources (pil64), as I studied them around 2017. It is the assembly implementation of cdr. PicoLisp is MIT-licensed, © Software Lab, Alexander Burger. Since 2020 the current PicoLisp is pil21, which is written in PicoLisp itself and compiled through LLVM, so the line-by-line details here belong to the older 64-bit assembly implementation; the ideas carry over. Current sources are at software-lab.de.

# (cdr 'lst) -> any
(code 'doCdr 2)
   push X
   ld X E
   ld E ((E CDR))  # Get arg
   eval
   cmp E Nil  # Need list
   if ne
      atom E
      jnz lstErrEX
   end
   ld E (E CDR)  # Take CDR
   pop X
   ret