Arithmetic operators with zero and one arguments

[camoy]

Some arithmetic operators (like + and *) cause an error when given 0 arguments.

(+)

Gives:

match: no matching clause for '()
  location...:
   /home/camoy/wrk/soft-contract/soft-contract/parse/private.rkt:522:7
  context...:
   .../private/runtime.rkt:82:34: fail-handler2403
   /home/camoy/wrk/racket/racket/collects/racket/contract/private/arrow-higher-order.rkt:375:33
   [repeats 1 more time]
   .../private/parse.rkt:626:19: success
   /home/camoy/wrk/soft-contract/soft-contract/parse/private.rkt:105:7: stx-map
   /home/camoy/wrk/soft-contract/soft-contract/parse/private.rkt:110:7: stxs->modules
   /home/camoy/wrk/soft-contract/soft-contract/parse/main.rkt:26:4: parse-files65
   /home/camoy/wrk/soft-contract/soft-contract/verifier.rkt:49:2: havoc105
   /home/camoy/wrk/soft-contract/soft-contract/cmdline.rkt:59:4
   body of "/home/camoy/wrk/soft-contract/soft-contract/cmdline.rkt"
   /home/camoy/wrk/racket/racket/collects/raco/raco.rkt:41:0
   body of "/home/camoy/wrk/racket/racket/collects/raco/raco.rkt"
   body of "/home/camoy/wrk/racket/racket/collects/raco/main.rkt"

Using arithmetic operators with arity 1 can give an unsound result.

(+ "hi")

Gives:

Safe