Wednesday, May 27, 2009

C++ references -- strict and clean rules

int i2; int & ri = i2;
Cat c; Cat & rc=c;

#1 keyword -- a reference is an *ALIAS* or symlink [1] to another variable

* you can take address-of ri. looks the same as i2 i.e.&ri === &i2
* ri can be a lvalue. looks the same as i2, i.e. "ri=222" === "i2=222". In fact, this also shows you can never reassign a reference to a second target object (different memory location).
* you never need to deference a reference. ri looks the same as i2, without the deref operator "&".
* when the target of the ref is a user-defined object, then the ref looks the same as the original handle on the object. See P168 [[24]].
* you can put ri on the RHS when initialize a new ref. ri works the same as i2 the original nonref variable.

[1] unix hardlinks have equal status to each other, unlike reference vs referent

A reference has no “separate identity” because it lacks an observable address. Compiler completely hides whatever address a reference occupies.

A reference must be seated at birth and will never be null or reseated. A reference is like your baby boy (Dabao). He has a mother at birth and can’t change his mother. However, a reference can become "invalid" when referent memory is reclaimed.

/*
* The following two lines won’t work because reference has to
* be initialized at the time of declaration
*/
int &debug_level_ref;
debug_level_ref = level;
- so always initialize references
- because references always need to be initialized there could be no NULL references
- references cannot be re-initialized, i.e. throughout its lifetime it will serve as
an alias to the object it was first initialized with

No comments:

Total Pageviews

my favorite topics (labels)

_fuxi (302) _misLabel (13) _orig? (3) _rm (2) _vague (2) clarified (58) cpp (39) cpp_const (22) cpp_real (76) cpp/java/c# (101) cppBig4 (54) cppSmartPtr (35) cppSTL (33) cppSTL_itr (27) cppSTL_real (26) cppTemplate (28) creditMkt (14) db (65) db_sybase (43) deepUnder (31) dotnet (20) ECN (27) econ/bank` (36) fin/sys_misc (43) finGreek (34) finReal (45) finRisk (30) finTechDesign (46) finTechMisc (32) finVol (66) FixedIncom (28) fMath (7) fMathOption (33) fMathStoch (67) forex (39) gr8IV_Q (46) GTD_skill (15) GUI_event (30) inMemDB (42) intuit_math (41) intuitFinance (57) javaMisc (68) javaServerSide (13) lambda/delegate (22) marketData (28) math (10) mathStat (55) memIssue (8) memMgmt (66) metaProgram` (6) OO_Design (84) original_content (749) polymorphic/vptr (40) productive (21) ptr/ref (48) py (28) reflect (8) script`/unix (82) socket/stream (39) subquery/join (30) subvert (13) swing/wpf (9) sysProgram` (16) thread (164) thread_CAS (15) thread_cpp (28) Thread* (22) timeSaver (80) transactional (23) tune (24) tuneDB (40) tuneLatency (30) z_ajax (9) z_algoDataStruct (41) z_arch (26) z_arch_job (27) z_automateTest (17) z_autoTrad` (19) z_bestPractice (39) z_bold (83) z_bondMath (35) z_book (18) z_boost (19) z_byRef^Val (32) z_c#GUI (43) z_c#misc (80) z_cast/convert (28) z_container (67) z_cStr/arr (39) z_Favorite* (8) z_FIX (15) z_forex (48) z_fwd_Deal (18) z_gz=job (33) z_gzBig20 (13) z_gzMgr (13) z_gzPain (20) z_gzThreat (19) z_hib (19) z_IDE (52) z_ikm (5) z_IR_misc (36) z_IRS (26) z_javaWeb (28) z_jdbc (10) z_jobFinTech (46) z_jobHunt (20) z_jobRealXp (10) z_jobStrength (15) z_jobUS^asia (27) z_letter (42) z_linq (10) z_memberHid` (11) z_MOM (54) z_nestedClass (5) z_oq (24) z_PCP (12) z_pearl (1) z_php (20) z_prodSupport (7) z_py (31) z_quant (14) z_regex (8) z_rv (38) z_skillist (48) z_slic`Problem (6) z_SOA (14) z_spring (25) z_src_code (8) z_swingMisc (50) z_swingTable (26) z_unpublish (2) z_VBA/Excel (8) z_windoz (17) z_wpfCommand (9)

About Me

New York (Time Square), NY, United States
http://www.linkedin.com/in/tanbin