Looks like unbound? and symbol-value take quoted symbols if passing them directly: And for list you have to use the transformed name scheme#list
#;2> (unbound? 'x) #t #;3> (define x 1) #;4> (unbound? 'x) #f #;5> (symbol-value 'x) 1 #;6> (symbol-value 'scheme#list) #<procedure (scheme#list . lst)> On Thu, Jun 22, 2023 at 10:15 PM Pan Xie <xie...@skyguard.com.cn> wrote: > Hello > > I am new to CHICKEN scheme and here is a (very) quick question of how to > check whether a symbol is bound. > > I know it doable but I can't find the way. > > I don't find the methods from the main CHICKEN manual document. Then I > import the "symbol-value-utils" module. I believe the "unbound?" or > "symbol-value" will do what I want, but to my surprise they does NOT: > > I expect `symbol-value' will give me value of a symbol, but it will > throw exception for an > undefined symbol, even I provide the default value: > > (symbol-value foo #f) > Error: unbound variable: foo > > I expect (symbol-value (string->symbol "list")) will give me the list > procedure, but what I get is '#f' > > (symbol-value (string->symbol "list")) > #f > > I expect (unbound? foo) will return True value, but it just throw > exception. > > Does CHICKEN scheme provide facilities that make user check whether > arbitrary symbol is bound or get its value, just like the `boundp' or > `symbol-value' in Common Lisp? > > Thanks > Pan > > >
