functionmethodssmalltalkgnu-smalltalk

Why this method's return part is not working

I am trying to write a method which returns a new value. Following code is modified from here: 

| stripChars |
stripChars := [ :string :chars |    
    str := string reject: [ :c | chars includes: c ].
    str displayNl.          "THIS WORKS."
    ^ str                   "THIS DOES NOT WORK."
].

newstr := stripChars 
    value: 'She was a soul stripper. She took my heart!'
    value: 'aei'.
newstr displayNl.

Although above function creates new string and displays it, there is error in returning or receiving returned new string: 

$ gst make_fn_ques.st
Sh ws  soul strppr. Sh took my hrt!
Object: 'Sh ws  soul strppr. Sh took my hrt!' error: return from a dead method context
SystemExceptions.BadReturn(Exception)>>signal (ExcHandling.st:254)
SystemExceptions.BadReturn class(Exception class)>>signal (ExcHandling.st:151)
String(Object)>>badReturnError (Object.st:1389)
UndefinedObject>>executeStatements (make_fn_ques.st:10)
nil

Where is the problem and how can this be solved? Thanks for your help.

Solution

  • The 

    ^ str

    does not return from the block (stripChars), but from the enclosing method instead (non-local return).

    Apparently GNU Smalltalk does not allow you to return from the script that you pass to gst in this way.

    Just drop the ^, and keep only str as the last expression of the block. That will cause str to be the return value of the block.