2012/2/28 Johannes Brauer <bra...@nordakademie.de> > Hi! > > In DrRacket version 5.02 this x-expression > > (validate-xexpr '(add x 2)) > > is legal. In version 5.2 I get the error message > > Expected a string, symbol, number, comment, processing instruction, or > list, given 2 > > Can anyone explain this to me? >
According to the grammar in the documentation a lone number is not an x-expression. Use '(add x "2") instead. xexpr = string | (list<http://docs.racket-lang.org/reference/pairs.html?q=xexpression#(def._((quote._~23~25kernel)._list))> symbol (list<http://docs.racket-lang.org/reference/pairs.html?q=xexpression#(def._((quote._~23~25kernel)._list))> (list<http://docs.racket-lang.org/reference/pairs.html?q=xexpression#(def._((quote._~23~25kernel)._list))> symbol string) ...) xexpr ...) | (cons<http://docs.racket-lang.org/reference/pairs.html?q=xexpression#(def._((quote._~23~25kernel)._cons))> symbol (list<http://docs.racket-lang.org/reference/pairs.html?q=xexpression#(def._((quote._~23~25kernel)._list))> xexpr ...)) | symbol | valid-char?<http://docs.racket-lang.org/xml/index.html?q=xexpression#(def._((lib._xml/main..rkt)._valid-char~3f))> | cdata | misc -- Jens Axel Søgaard
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