Declaring variables (or words or whatever)

[1/3] from: Steven:White:ci:bloomington:mn:us at: 3-Jun-2003 13:20

I'm having a terrible time getting out of my old ways of thinking. If I want to declare a variable, just because I like to do things that way because it helps me keep track of things, which of these ways is recommended, or they equivalent? TP-FILE-ID: make file! %TPLAYER.DAT ;;; (number one) ... or ... make file! TP-FILE-ID: %TPLAYER.DAT ;;; (number two) ... or ... TP-FILE-ID: %TPLAYER.DAT ;;; (number three) They all seem to work, that is, if I "print TP-FILE-ID" I get the same results, but is one better/more efficient/recommended/better style etc.? Thank you. Steven White City of Bloomington 2215 W Old Shakopee Rd Bloomington MN 55431-3096 USA 952-563-4882 (voice) 952-563-4672 (fax) [swhite--ci--bloomington--mn--us]

[2/3] from: joel::neely::fedex::com at: 3-Jun-2003 14:33

Hi, Steven, Steven White wrote:

> If I want to declare a variable, just because I like to do things that > way because it helps me keep track of things,... >

That concept (in the sense that c-like languages use it) simply doesn't exist. Values have types, and there's no way to require that a given word be set only to values of a specific type. foo: "I have" foo: 5.0 foo: #toes foo: %per foo: 1.0 foo: 'foot REBOL is perfectly willing for all of those expressions to be evaluated one after the other. If, on the other hand, you want to manage the scope of words, and/or avoid cluttering up the global namespace, you could wrap each script (or other meaningful unit of code) in an object, so that the explicit setting of the words during the creation of the object serves both to initialize them and to give you a consolidated "reminder list" of the names you intend to use. However, this is purely a matter of choice and convention. Comments would also work as well. That said...

> TP-FILE-ID: make file! %TPLAYER.DAT ;;; (number one) > make file! TP-FILE-ID: %TPLAYER.DAT ;;; (number two)

<<quoted lines omitted: 3>>

> recommended/better style > etc.?

Among those three, the last is the most reasonable, because

>> type? %tplayer.dat

== file! the value %tplayer.dat is *already* of the FILE! datatype, so the extra conversions are as pointless as saying foo: make integer! 3 to obtain an integer result. The first one does the redundant conversion before setting the word. The second actually has no effect at all (unless wrapped in a larger expression which uses the resulting value) as TP-FILE_ID is already set to the "literal" FILE! value. The result of that setting operation is a reference to the same FILE! value, which is then (re-)converted to a FILE! value. Unless there's a surrounding expression which does something else with *that* value, it's effectively discarded when the next expression begins. HTH! -jn- -- ---------------------------------------------------------------------- Joel Neely joelDOTneelyATfedexDOTcom 901-263-4446 Counting lines of code is to software development as counting bricks is to urban development.

[3/3] from: greggirwin:mindspring at: 3-Jun-2003 14:30

Hi Steven, SW> I'm having a terrible time getting out of my old ways of thinking. SW> If I want to declare a variable, just because I like to do things that SW> way because it helps me keep track of things, which of these ways is SW> recommended, or they equivalent? SW> TP-FILE-ID: make file! %TPLAYER.DAT ;;; (number one) SW> ... or ... SW> make file! TP-FILE-ID: %TPLAYER.DAT ;;; (number two) SW> ... or ... SW> TP-FILE-ID: %TPLAYER.DAT ;;; (number three) SW> They all seem to work, that is, if I "print TP-FILE-ID" I get the same SW> results, but is one better/more efficient/recommended/better style SW> etc.? I'd use #3 for all general cases. While I don't agree *entirely* with the Agile motto of "Do the simplest thing possible", in this case it works. REBOL understands the value directly, so there is no need to do anything special. In #2 you're just discarding the value returned by MAKE, so it's entirely redundant. Now, #1 doesn't behave exactly like #3, so that's the other thing to consider, and what is one of the hardest things to remember about REBOL when coming from other languages. How you define values, and how you use them, needs to be considered. E.g. print f-1: make file! f-2: f-3: %TPLAYER.DAT f-4: %TPLAYER.DAT print equal? f-1 f-2 print same? f-1 f-2 print same? f-2 f-3 print same? f-2 f-4 append f-2 "XXX" print [f-1 f-2 f-3 f-4] -- Gregg

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