Stylistic Conventions and Design Philosophy

Stylistic Conventions

• Objective-C source files have file extension `.m'. Both C-compatibility header files and class declaration files have extension `.h'.
• Objective-C class names begin with capital letters. Multi-word class names capitalize each word, with no underscore separation.
• Include files that define Objective-C classes begin with capital letters (as do the names of the classes themselves).
• All protocols end with ing. All collection protocols end with Collecting. All collection abtract superclasses (classes which are not usable without subclassing) end with Collection.
• Include files that supply function prototypes for other C functions are all lower case.
• Instance variables begin with an underscore, are all lower case, and have underscores separating their component words. The leading underscore distinguishes them from local varibles defined inside methods.
• All include files define a preprocessor variable __X_h_INCLUDE_GNU, where X is the name of the file, and conditionally compile only if this has not been already defined.
• The following macros and variables make the relevant version numbers available:

  Macro: COLL_VERSION

  The version number of the collection library. Declared in `coll/collstd.h'

  Macro: COLL_GCC_VERSION

  The version number of the compiler used to compile the collection library. Declared in `coll/collstd.h'

  Variable: char[] coll_version

  A string containing the version number of the collection library. Declared in `coll/collstd.h'

  Variable: char[] coll_gcc_version

  A string containing the version number of the compiler used to compile the collection library. Declared in `coll/collstd.h'

The design philosophy.

Objective-C is not Smalltalk. Differences that matter to the Collection heirarchy:

• There can be only one set of argument types with each selector. (For instance in Objective-C we can't have "-(double)data" and "-(char)data". I can't stand it when some library that I'm forced to load already defines a selector that I want to use with different types.) This isn't an issue in Smalltalk because everything is an object. I make the Collection method names a little more descriptive, while keeping them close to Smalltalk. (For instance I think there is a good reason for using "-addObject:" instead of "-add:")
• We will want collections of int's, float's, and other non-Objects. Using Objective C wrappers around these C primitive types (i.e. Integer and Float objects) is not an efficient enough option for all cases. We could create two parallel heirarchies, one for Objects and one for elements passed as void*, but since so much of the functionality overlaps, I have merged them, and it doesn't actually look all that bad.
• Objective C doesn't have Smalltalk Blocks. Passing pointers to functions is a reasonable substitute. This is made easier with gcc's nested functions and the LAMBDA() macro defined in coll/collstd.h.
• Smalltalk does automatic garbage collection; Objective C doesn't. I think it should be made obvious which methods allocate a new object. Hence "-shallowCopyAs:[Bag class]" instead of "as:[Bag class]".
• We have usable Collection classes (Set, Bag, Array, etc) with functionality matching Smalltalk's objects, but there are good reasons for not having the abstract superclass structure match Smalltalk exactly.

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