readline - read and edit a line from standard input
any readline -> any true
-> false
readline takes anything from the prompt as a string and prints it.
If something is added, readline pushes the additional phrase as string
plus a true on the stack (that means readline reads a line from
standard input). If nothing is added false is pushed.
docu by Sirko Straube
/var/www/debian/nest/nest-simulator-2.20.0/lib/sli/sli-init.sli