This experiment finds out whether 1+x and 1+ are valid identifiers in the Scheme implementations. They are invalid in all versions of the Scheme standard. We also investigate whether 1+ and add1 are known procedures.

1+x is valid, 1+ is defined, add1 is defined: Chez, Sizzle

1+x is valid, 1+ is not defined, add1 is defined: Racket, Chicken, SISC

1+x is valid, 1+ is defined, add1 is not defined: MIT, Guile, SCM, XLisp, Rep, Elk, FemtoLisp, Inlab

1+x is valid, 1+ is not defined, add1 is not defined: Gauche, Gambit, Bigloo, Kawa, JScheme, STklos, Shoe, TinyScheme, Scheme 9, BDC, Schemik, Llava, Sagittarius

1+x and 1+ are syntax errors, add1 is defined: Vicare, IronScheme, RScheme, SXM

1+x and 1+ are syntax errors, add1 is not defined: Scheme48/scsh, Larceny, Ypsilon, Mosh, KSi, SigScheme, UMB, Dfsch, Foment, Chibi

1+x is read as 1 +x, 1+ is read as 1 +, add1 is not defined: NexJ, Picrin, Owl Lisp