Popular Myths about C++, Part 1

Post by pjmlp » Tue, Dec 09, 2014, 8:35 PM UTC

WhitneyLand wrote: post #43

Does anyone choose C++ anymore unless it is required by environment/legacy/performance constraints? Back in the day I read Bjarne's book cover to cover, used C++ for very large scale projects, and was one of those guys who could make sense of arbitrarily complex pointer expressions. Now I mostly regret it. Led down the rabbit hold of multiple inheritance, STL being much more complicated than templating in other langu…

Post by humanrebar » Tue, Dec 09, 2014, 8:53 PM UTC

Retra wrote: post #98

humanrebar wrote: post #50

Earlier quoted context omitted.

To be fair everything you're upset about is a problem with the standard C++ library, not the language itself. Not to say that the language doesn't have issues. The initializer list example you provide is half of one, but only because people don't like to write algorithm-based code. This is actually fine: auto v = {1, 2, 3, 5, 8, 13}; for (auto i : v) { std::cout ...all that being said, the C++ standard library gets s…

Standard libraries are part of the language. I would go so far as to say anybody who designs a language that isn't meant to make their standard libraries powerful, consistent, and elegant isn't doing any favors for the discipline.

Post by maxlybbert » Tue, Dec 09, 2014, 9:56 PM UTC

mike-cardwell wrote: post #107

maxlybbert wrote: post #75

Earlier quoted context omitted.

Try it with optimizations on: gcc -std=c99 -O3 -Wall -Wextra test.c -o test g++ -std=c++11 -O3 -Wall -Wextra test.cpp -o test In my experience, C++ compilers are great at eliding temporaries and various constructor calls (and related memory allocations), but only if optimizations are turned on.

Made no difference

Post by pjmlp » Tue, Dec 09, 2014, 10:33 PM UTC

throwawayaway wrote: post #58

pjmlp wrote: post #57

Earlier quoted context omitted.

By using them like safe system programming languages from Algol/Mesa line do. Out function parameters are implicit pointers via references. Cannot be null. Pointers and arrays aren't compatible. Pointer arithmetic is frown upon and in many of those languages requires an explicit unsafe block/system module import.

would it be fair to say you have just described references, or do I have to go and lookup this algol/mesa stuff?

    MODULE examples;
    IMPORT Terminal, SYSTEM;

    (* procedure with reference parameter, no need for pointers *)
    PROCEDURE ChangeParam (VAR changeMe: CARDINAL);
    BEGIN
      changeMe := 25;
    END ChangeParam;

    (* 
       procedure with a slice, bounds given by HIGH(changeMe) and LOW(changeMe).
       also a string in this case
       no need for explicit pointers
    *)
    PROCEDURE DumpLetters (VAR letters: ARRAY OF CHAR);
    VAR
      i : CARDINAL;
      
    BEGIN
      FOR i := 0 TO HIGH(letters) DO
         WriteChar(letters[i]);
      WriteLn;
      (* Or just use *)
      WriteString (letters);
    END DumpLetters;


    VAR
      anInt : CARDINAL := 12 ;
      aPtr : POINTER TO CHAR;
      aBuffer : ARRAY [1..2] OF CHAR;
      anAddr : ADDRESS; (* think void* *)
      aPtr2 : POINTER TO CHAR;
      
    BEGIN
      WriteInt(anInt); (* writes 12 *)
      ChangeParam (anInt);
      WriteInt(anInt); (* writes 25 *)
      DumpLetters ('A simple string');
      NEW(aPtr); (* The compiler knows the size, no need for sizeof, but you can use ALLOCATE(aPTR, SIZE(CHAR)) if you want *)
      
      (* This is where it shares the same problems with C, due to manual memory control  *)
      DISPOSE(aPtr); 
      
      (* do pointer arithmetic if really required *)
      anAddr := SYSTEM.ADDADR (SYSTEM.ADR(aBuffer), SIZE(CHAR) * 1); 
      aPtr2 := SYSTEM.CAST(POINTER TO CHAR, anAddr); (* aPtr2 now points to aBuffer(2) *)
    END examples;

Post by throwawayaway » Tue, Dec 09, 2014, 11:51 PM UTC

pjmlp wrote: post #110

throwawayaway wrote: post #63

Earlier quoted context omitted.

ok: why do structs exist and why are their members public? why don't you just use classes with public? i have been taught extremely poorly and am many years your junior. K&R/stan lipmann's "inside the C++ object model" was a huge "oh ok, I've been basically lied to the entire time"

> why do structs exist and why are their members public? why don't you just use classes with public? To be able to reuse existing C code in a C++ compiler, while allowing them to participate in class hierarchies. This is the real reason, but you don't need to explain it like that to new C++ devs. Use struts when you just need a data container. Use classes when you need to add behaviour. Simple rule, no need to talk a…