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digitalmars.D - Re: C++ traps that D2 doesn't avoid yet?

reply ore-sama <spam here.lot> writes:
bearophile Wrote:


 This page lists a lot of C++ traps and pitfalls in a short space. I assume D
has to avoid or render meaningless a quite high percentage of them.
 The nice thing of that list is that I think most (maybe 80-90%) of those traps
and pitfalls (and several others that aren't listed, like allowing simple
syntactical mistakes like putting a & where a && was requires or vice versa,
etc) can be avoided by a language like D
 but seeing the huge troubles C++ has gone to be as much compatible as possible
with C I'd say that keeping the original C semantics when it is known to cause
troubles is _always_ bad. In such situations I prefer a language that acts
correctly



Most of these pitfalls are actually features, not bugs and are used massively.
Like implicit casts, & instead of &&, assignment instead of comparison etc.
These are pitfalls for novice programmers. Why bother? Everything is a pitfall
for a novice programmer. You can safely say that every feature is a pitfall
because programmer can make mistake in any place. I saw a man writing a program
randomly typing something on the keyboard :) And he's not alone. What will be a
pitfall for such programmers?

ps why there was a need to reinvent identity operator, I wonder? It already was
in JavaScript.
Nov 06 2008
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"ore-sama" wrote

 bearophile Wrote:


 This page lists a lot of C++ traps and pitfalls in a short space. I 
 assume D has to avoid or render meaningless a quite high percentage of 
 them.
 The nice thing of that list is that I think most (maybe 80-90%) of those 
 traps and pitfalls (and several others that aren't listed, like allowing 
 simple syntactical mistakes like putting a & where a && was requires or 
 vice versa, etc) can be avoided by a language like D
 but seeing the huge troubles C++ has gone to be as much compatible as 
 possible with C I'd say that keeping the original C semantics when it is 
 known to cause troubles is _always_ bad. In such situations I prefer a 
 language that acts correctly



 Most of these pitfalls are actually features, not bugs and are used 
 massively. Like implicit casts, & instead of &&, assignment instead of 
 comparison etc. These are pitfalls for novice programmers. Why bother?



They can be made more difficult to do mistakenly.

Even experienced developers fall into some of these traps.  I know I 
occasionally fell into this trap:

if(x);
  x->doSomething();

But no more with D, because it's not allowed.  Those kinds of things can be 
easily prevented, and are common mistakes by all programmers.

I appreciate any effort by the compiler to not compile code that can be 
definitively declared as invalid.  It saves me time and bugs, and that is 
worth a lot.

-Steve
Nov 06 2008
next sibling parent reply ore-sama <spam here.lot> writes:
Steven Schveighoffer Wrote:


 I appreciate any effort by the compiler to not compile code that can be 
 definitively declared as invalid.  It saves me time and bugs, and that is 
 worth a lot.



You said "definitely". Your example is meaningful, but this doesn't affect my
examples.
Nov 06 2008
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"ore-sama" wrote

 Steven Schveighoffer Wrote:


 I appreciate any effort by the compiler to not compile code that can be
 definitively declared as invalid.  It saves me time and bugs, and that is
 worth a lot.



 You said "definitely". Your example is meaningful, but this doesn't affect 
 my examples.



Yes, you are probably right.  Those can be valid either way, much more than 
my example.

To be honest though, I more disagree with your assertion that only novice 
programmers are affected.  I sometimes make these types of mistakes, and I 
definitely don't consider myself a novice ;)

-Steve
Nov 06 2008
next sibling parent Walter Bright <newshound1 digitalmars.com> writes:
Steven Schveighoffer wrote:

 To be honest though, I more disagree with your assertion that only novice 
 programmers are affected.  I sometimes make these types of mistakes, and I 
 definitely don't consider myself a novice ;)



The if(e); is illegal in D because back in the 80's, the best programmer 
in the company came to me asking me why his for loop executed only once:

    for (i = 0; i < N; i++);
         ...

He had spent all afternoon chasing this problem, first isolating it to 
the loop and then trying to figure it out. He was sure it was a compiler 
bug. I stared at it for a while, mystified too, until I saw the ;.

There is no advantage to having the language accept such code, and even 
if the programmer wrote it on purpose, it *looks* like a bug. Code that 
looks right should be right, and code that looks wrong should be wrong.
Nov 06 2008
prev sibling parent reply Janderson <ask me.com> writes:
Steven Schveighoffer wrote:


 To be honest though, I more disagree with your assertion that only 



mistakes, and I definitely don't consider myself a novice ;)

 -Steve



A good point.

We seem to have a lot of super programmers who don't make simple 
mistakes ever and know C++ back to front.  That's Great!

For myself, after programming in C++ for 7 years (and other languages 
before that) I still find myself making coding typo's and discovering 
new things about C++.  Keeping an open mind is key to getting better.

I bet even Bjarne Stroustrup himself does not know all the pitfalls he 
left in the language.

A couple of quotes to put names to:

"Anyone who has never made a mistake has never tried anything new."

"...it's essential to keep an open mind, and to be willing--better yet, 
eager--to try new things."

"The trouble with having an open mind, of course, is that people will 
insist on coming along and trying to put things in it."

-Joel
Nov 08 2008
next sibling parent reply ore-sama <spam here.lot> writes:
Janderson Wrote:


 We seem to have a lot of super programmers who don't make simple 
 mistakes ever and know C++ back to front.  That's Great!



Who knows C++? I know C, C# and javascript.


 For myself, after programming in C++ for 7 years (and other languages 
 before that) I still find myself making coding typo's and discovering 
 new things about C++.  Keeping an open mind is key to getting better.



Yeah, C++ is a continuous discovery, may be because of this C++ pros can't get
used to if statement syntax? I thought, fingers know syntax, not brain... well,
it's C++ after all :3
Nov 09 2008
parent Janderson <ask me.com> writes:
ore-sama wrote:

 Janderson Wrote:
 

 We seem to have a lot of super programmers who don't make simple 
 mistakes ever and know C++ back to front.  That's Great!



 Who knows C++? I know C, C# and javascript.



I see then this kinda makes sense from where your coming from.  C# has a 
load of restrictions that help detect possible gotchas that you don't 
get with C++.  They could be removed to allow for more "expressive" code 
but then you'd have C++.  For example, trying to change the size of an 
array your iterating over will flag an error in C#.


 

 For myself, after programming in C++ for 7 years (and other languages 
 before that) I still find myself making coding typo's and discovering 
 new things about C++.  Keeping an open mind is key to getting better.



 Yeah, C++ is a continuous discovery, may be because of this C++ pros can't get
used to if statement syntax? I thought, fingers know syntax, not brain... well,
it's C++ after all :3
Nov 09 2008
prev sibling parent Walter Bright <newshound1 digitalmars.com> writes:
Janderson wrote:

 "The trouble with having an open mind, of course, is that people will 
 insist on coming along and trying to put things in it."



"An open mind is an empty mind." -- Mark Stroberg
Nov 09 2008
prev sibling next sibling parent reply Walter Bright <newshound1 digitalmars.com> writes:
Steven Schveighoffer wrote:

 Even experienced developers fall into some of these traps.  I know I 
 occasionally fell into this trap:
 
 if(x);
   x->doSomething();
 
 But no more with D, because it's not allowed.  Those kinds of things can be 
 easily prevented, and are common mistakes by all programmers.



Here's another fun one:

     printf("%d\n", 8l);

What does that print?
Nov 06 2008
next sibling parent reply BCS <ao pathlink.com> writes:
Reply to Walter,


 Steven Schveighoffer wrote:
 

 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:
 
 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.
 



 
 printf("%d\n", 8l);
 
 What does that print?
 



8
Nov 06 2008
next sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"BCS" wrote

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?



 8



On little endian systems, yes.  On big endian it would print 0.

-Steve
Nov 06 2008
prev sibling parent reply Walter Bright <newshound1 digitalmars.com> writes:
BCS wrote:

 Reply to Walter,
 

 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?



 8



If I hadn't said it was a trap, I bet you'd have said "81".
Nov 06 2008
next sibling parent reply Walter Bright <newshound1 digitalmars.com> writes:
Jarrett Billingsley wrote:

 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?









 I wouldn't've, because I use a font that actually distinguishes things
 1, I, l, and | properly.  <_<



0 and O is another fun one. In any case, 8l is legal C, but illegal D.
Nov 06 2008
next sibling parent bearophile <bearophileHUGS lycos.com> writes:
Jarrett Billingsley:

 ProggyCleanSZ, thankyouverymuch.  Code doesn't look like code unless
 it's in that font ;)



I use this (it's free) and I'm very happy of it, but note it requires a bigger
size than Proggy, so if you want to program with a little font this isn't good:
http://www.levien.com/type/myfonts/inconsolata.html

Bye,
bearophile
Nov 06 2008
prev sibling next sibling parent Don <nospam nospam.com> writes:
Walter Bright wrote:

 Jarrett Billingsley wrote:

 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?









 I wouldn't've, because I use a font that actually distinguishes things
 1, I, l, and | properly.  <_<



 0 and O is another fun one. In any case, 8l is legal C, but illegal D.



In CompSci1 we had use some ridiculous Mac editor where 0 and O were 
100% identical, I,l, | and 1 also. It was an incredible source of bugs.
We had to write a parser/emulator for some stupid imaginary asm language 
they'd invented, where O01 was output register 1. Plus, whitespace was 
significant, but it wasn't a monospaced font...
It was like the whitespace programming language.
Nov 07 2008
prev sibling next sibling parent reply Lars Kyllingstad <public kyllingen.NOSPAMnet> writes:
Bill Baxter wrote:

 On Fri, Nov 7, 2008 at 7:37 AM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 Jarrett Billingsley wrote:

 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?









 1, I, l, and | properly.  <_<






 Threre are various good programmer fonts out there today that are
 designed to make the 1 l | and 0 O distinctions clear.
 I use the Proggy fonts.  http://www.proggyfonts.com/index.php?menu=download
 
 These days I'd say if you're not using one of these fonts for
 programming you're being an extremely silly person.
 
 --bb



I use and recommend the DejaVu Sans Mono font. With this font there is 
no chance of confusing those troublesome characters, and it's very easy 
on the eyes. Also, the DejaVu fonts are available in the repositories of 
many (most?) Linux distributions.

    http://dejavu.sourceforge.net/

-Lars
Nov 07 2008
parent Mike Parker <aldacron gmail.com> writes:
Lars Kyllingstad wrote:

 Bill Baxter wrote:

 On Fri, Nov 7, 2008 at 7:37 AM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 Jarrett Billingsley wrote:

 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I 
 know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of 
 things
 can be easily prevented, and are common mistakes by all 
 programmers.




 printf("%d\n", 8l);

 What does that print?









 1, I, l, and | properly.  <_<






 Threre are various good programmer fonts out there today that are
 designed to make the 1 l | and 0 O distinctions clear.
 I use the Proggy fonts.  
 http://www.proggyfonts.com/index.php?menu=download

 These days I'd say if you're not using one of these fonts for
 programming you're being an extremely silly person.

 --bb



 I use and recommend the DejaVu Sans Mono font. With this font there is 
 no chance of confusing those troublesome characters, and it's very easy 
 on the eyes. Also, the DejaVu fonts are available in the repositories of 
 many (most?) Linux distributions.
 
    http://dejavu.sourceforge.net/
 
 -Lars



I was surprised to learn I already have several versions of Deja Vu 
installed (on Windows). I've configured all of my text editors and even 
Thunderbird to use it now. What a difference! Thanks for pointing it out.
Nov 07 2008
prev sibling parent Walter Bright <newshound1 digitalmars.com> writes:
Bill Baxter wrote:

 These days I'd say if you're not using one of these fonts for
 programming you're being an extremely silly person.



That's great, but one doesn't always have control over the fonts.
Nov 07 2008
prev sibling parent reply Derek Parnell <derek psych.ward> writes:
On Thu, 6 Nov 2008 17:14:13 -0500, Jarrett Billingsley wrote:


 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?



 8



 If I hadn't said it was a trap, I bet you'd have said "81".



 I wouldn't've, because I use a font that actually distinguishes things
 1, I, l, and | properly.  <_<



Same here. I thought the 'trap' was using %d with a *long* value.

-- 
Derek Parnell
Melbourne, Australia
skype: derek.j.parnell
Nov 07 2008
parent "Nick Sabalausky" <a a.a> writes:
"Derek Parnell" <derek psych.ward> wrote in message 
news:16rwvaqsxxzdx.hzsh3le743yv$.dlg 40tude.net...

 On Thu, 6 Nov 2008 17:14:13 -0500, Jarrett Billingsley wrote:


 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?



 8



 If I hadn't said it was a trap, I bet you'd have said "81".



 I wouldn't've, because I use a font that actually distinguishes things
 1, I, l, and | properly.  <_<



 Same here. I thought the 'trap' was using %d with a *long* value.



In my newsgroup client, the lower-case 'L' renders as a straight vertical 
line with no serif or anything else. I can't remember ever seeing a 
(non-oddball) font where the "one" digit looked like that, so I 
instinctively saw it as "8L" and thought the intended gotcha was a 
mismatched number of bits causing a zero on a system of the wrong 
endianness. That said, I do still like D's requirement that the "L" suffix 
be capitalized.
Nov 07 2008
prev sibling next sibling parent "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
<newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?



 8



 If I hadn't said it was a trap, I bet you'd have said "81".



I wouldn't've, because I use a font that actually distinguishes things
1, I, l, and | properly.  <_<
Nov 06 2008
prev sibling next sibling parent "Bill Baxter" <wbaxter gmail.com> writes:
On Fri, Nov 7, 2008 at 7:37 AM, Walter Bright
<newshound1 digitalmars.com> wrote:

 Jarrett Billingsley wrote:

 On Thu, Nov 6, 2008 at 5:07 PM, Walter Bright
 <newshound1 digitalmars.com> wrote:

 BCS wrote:

 Reply to Walter,


 Steven Schveighoffer wrote:


 Even experienced developers fall into some of these traps.  I know I
 occasionally fell into this trap:

 if(x);
 x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things
 can be easily prevented, and are common mistakes by all programmers.




 printf("%d\n", 8l);

 What does that print?






 If I hadn't said it was a trap, I bet you'd have said "81".



 I wouldn't've, because I use a font that actually distinguishes things
 1, I, l, and | properly.  <_<



 0 and O is another fun one. In any case, 8l is legal C, but illegal D.



Threre are various good programmer fonts out there today that are
designed to make the 1 l | and 0 O distinctions clear.
I use the Proggy fonts.  http://www.proggyfonts.com/index.php?menu=download

These days I'd say if you're not using one of these fonts for
programming you're being an extremely silly person.

--bb
Nov 06 2008
prev sibling parent "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Thu, Nov 6, 2008 at 7:02 PM, Bill Baxter <wbaxter gmail.com> wrote:

 Threre are various good programmer fonts out there today that are
 designed to make the 1 l | and 0 O distinctions clear.
 I use the Proggy fonts.  http://www.proggyfonts.com/index.php?menu=download

 These days I'd say if you're not using one of these fonts for
 programming you're being an extremely silly person.



ProggyCleanSZ, thankyouverymuch.  Code doesn't look like code unless
it's in that font ;)
Nov 06 2008
prev sibling next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Thu, 06 Nov 2008 23:34:55 +0300, Walter Bright  
<newshound1 digitalmars.com> wrote:


 Steven Schveighoffer wrote:

 Even experienced developers fall into some of these traps.  I know I  
 occasionally fell into this trap:
  if(x);
   x->doSomething();
  But no more with D, because it's not allowed.  Those kinds of things  
 can be easily prevented, and are common mistakes by all programmers.



 Here's another fun one:

      printf("%d\n", 8l);

 What does that print?



Yay, it is hardly distiguishable even at 500% zoom (Courier New)!
Nov 06 2008
prev sibling parent bearophile <bearophileHUGS lycos.com> writes:
Steven Schveighoffer:

 Even experienced developers fall into some of these traps.  I know I 
 occasionally fell into this trap:
 if(x);
   x->doSomething();
 But no more with D, because it's not allowed.  Those kinds of things can be 
 easily prevented, and are common mistakes by all programmers.



In Delight it's also quite difficult to fall in that trap:
if x:
    x->doSomething()
Many variants of that syntax are all disallowed:
if x
    x->doSomething()
if x:
x->doSomething()
if x
x->doSomething()
etc.

So instead of making the language more confusing, it actually has the opposite
effect.

Bye,
bearophile
Nov 06 2008
prev sibling parent bearophile <bearophileHUGS lycos.com> writes:
ore-sama:

 These are pitfalls for novice programmers. Why bother?<



I want D to be a little more novice-friendly than C++.
After 8 hours of coding, when I'm tired, I'm a novice myself, and I can
appreciate any help the compiler can offer.

Bye,
bearophile
Nov 06 2008