This experiment finds out whether +1x is a valid identifier in the Scheme implementations. It is invalid in all versions of the Scheme standard. We also investigate whether add1 is a known procedure.
+1x valid, add1 exists: Racket, Chicken, SISC, Sizzle
+1x valid, add1 does not exist: Gauche, MIT, Gambit, Bigloo, Guile, Kawa, SCM, Ypsilon, JScheme, STklos, Shoe, TinyScheme, Scheme 9, BDC, XLisp, Rep, Schemik, Elk, Llava, FemtoLisp, Inlab, Chibi
Syntax error, add1 exists: Vicare, IronScheme, RScheme, SXM
Syntax error, add1 does not exist: Scheme48/scsh, Larceny, Mosh, KSi, SigScheme, UMB, Dfsch, Foment
1+x is treated as 1 +x, add1 does not exist: NexJ, Picrin, Owl Lisp