Hi Bing Liang, Thanks for your comments. Fresh eyes provide interesting perspectives on things we take for granted.
On Sat, Feb 11, 2017 at 4:41 PM, lb <liangbin...@126.com> wrote: > Thank you, Sven > gradually clear. > 1. Symbol as String subclass, only guarantees a symbol object only one in > system, use ==; > 2. keywords (selector name method name) are spectial symbols, without space > or forbided characters; > 3. perform: aSymbol, means perform: aKeyword, Not exactly. It means perform a "message" where there are three types of messages... * unary, like #printString * binary, like #+ * keyword, like #perform: or #subclass:instanceVariableNames:classVariableNames:package: having a colon appended to each keyword > Should we add asKeyword to String, > let > perform: aString asKeyword or alternatively per above... perform: aString asMessage > not > perform: aString asSymbol ? In the case that aString contained a space, presumably #asMessage would produce a runtime error in asMessage whereas #asSymbol would produce a runtime error in #perform: I guess there is a minor benefit of failing early but will that make much difference in practice. Do you have a use case where it makes a major difference? > At 2017-02-11 15:51:49, "Sven Van Caekenberghe" <s...@stfx.eu> wrote: >>Hi Bing, >> >>Yes, any character is allowed in a Symbol. There is even special syntax >> that allows such Symbols to be represented literally. >> >>'a b' asSymbol. >> >> => #'a b' >> >>Although it might be confusing, I don't see any problem. >> >>The concept of 'meaning' is defined by the user, the usage, not by the >> Symbol itself. A Symbol with a space cannot be a selector (message/method) >> name, but that does not mean a Symbol with a space could not be useful in >> some other context. >> >>> On 11 Feb 2017, at 05:56, lb <liangbin...@126.com> wrote: >>> >>> Hi, >>> I know Symbol is subclass of String. >>> Any string object can become symbol object by sending 'asSymbol' >>> message.. >>> I think symbol must has its meaning in common use, so the symbol should >>> be composed of alphabet or number ‘without space“. Different domains have different common usage. IIUC, Smalltalk's definition of symbol is from the 1970s. Pharo is not overly constrained by Smalltalk traditions, but there must be sufficient gain to balance deviations from consistency with other Smalltalks. >>> >>> BUT There are not compliant below >>> 1. ' ' asSymbol >>>> no meaning >>> 2. '$%%&' asSymbol >>>> no meaning >>> 3. 'sign' asSymbol = 'sign ' asSymbol >>> false because of space. >>> 3. ' one two three ' asSymbol >>> I think It should >>> become three symbols = #one, #two, #three >>> >>> >>> Maybe my understanding is wrong. no problem. Being wrong is a great way to learn ;) cheers -ben
