Welcome to DrScheme, version 352.
Language: Typedscm, typed extension to EoPL(2e).
Teachpack: C:\cygwin\usr\local\PLT\collects\teachpack\drscheme-342-teachpack.scm.
> (force-at-surface 1)
. reference to undefined identifier: force-at-surface
> (import grav-force-mod)
. reference to undefined identifier: import
> (require "grav-force-mod")
open-input-file: cannot open input file: "C:\cygwin\usr\local\PLT\collects\lib342\grav-force-mod" (The system cannot find the file specified.; errno=2)
> (require (lib "grav-force-example.scm" "lib342"))
> (force-at-surface 1)
9.79700272815321
> (define force-of-1 (grav-force-c 1))
> ((force-of-1 1) 1)
6.67e-011
> (define sum-of-list
    (lambda (lon)
      (if (null? lon)
          0
          (+ (car lon) (sum-of-list (cdr lon))))))
> (sum-of-list '(3 4 2))
9
> (define sum
    (lambda args
      (sum-of-list args)))
> (sum 3 4 2 5 7)
21
> (sum )
0
> (sum 2 3)
5
>