PrintOutput:
; prints the output of the function "foo" to the screen.
; input:
; A = input for the function "foo".
; z_L = contains the low byte of the memory address of "foo"
; z_H = contains the high byte of the memory address of "foo"

pha

LDA z_L
STA smc+1  ;store in the low byte of the operand
LDA z_H
STA smc+2  ;store in the high byte of the operand

pla

smc:
JSR $1234
;uses self-modifying code to overwrite the destination with the address of the passed function.
;assuming that function ends in an RTS, execution will return to this line after the function is done.
JSR PrintAccumulator

rts