Hi 

I'm implementing a visitor based pretty printer
can somebody explain to me what is a selector containing only the character
: (as shownin the MessageNode method)?



MessageNode>>printOn: aStream indent: level

    | leadingKeyword |

"may not need this check anymore - may be fixed by the #receiver: change"
    special ifNil: [^aStream nextPutAll: '** MessageNode with nil special
**'].


    (special > 0)
        ifTrue: [self perform: self macroPrinter with: aStream with: level]
        ifFalse: [selector key first = $:
                ifTrue: [leadingKeyword _ selector key keywords first.
                        aStream nextPutAll: leadingKeyword; space.
                        self printReceiver: receiver on: aStream indent:
level.
                        self printKeywords: (selector key allButFirst:
leadingKeyword size + 1) arguments: arguments
                            on: aStream indent: level]
                ifFalse: [(aStream dialect = #SQ00 and: [selector key ==
#do:])
                        ifTrue: ["Add prefix keyword"
                                aStream withStyleFor: #prefixKeyword do:
[aStream nextPutAll: 'Repeat '].
                                self printParenReceiver: receiver on:
aStream indent: level + 1.
                                self printKeywords: selector key arguments:
arguments
                                    on: aStream indent: level prefix: true]
                        ifFalse: [self printReceiver: receiver on: aStream
indent: level.
                                self printKeywords: selector key arguments:
arguments
                                    on: aStream indent: level]]]