RE: [Dev-C++] Syntax problem??? Parser error??

[P.D. v. Z. <pa...@my...>]

It gets checked. The "this" pointer passed to const member functions is
const as well, so any attempt to modify member variables (or call non-const
member functions) will result in errors.
 

-----Original Message-----
From: dev...@li...
[mailto:dev...@li...] On Behalf Of Alvin
Thompson
Sent: Tuesday, October 28, 2003 8:20 PM
To: Per Westermark
Cc: de...@li...; dev...@li...
Subject: Re: [Dev-C++] Syntax problem??? Parser error??

i didn't know that either. does the compiler actually check the code to 
see if it tries to modify the List (and generate a compile error if it 
does), or is it more like a "gentleman's agreement"?

-alvin


Per Westermark wrote:

> you have a class
> 
> class List {
> public:
> 	bool isEmpty();
> };
> 
> If you rewrite it to:
> 
> class List {
> public:
> 	bool isEmpty() const;
> };
> 
> you tell the compiler that isEmpty() will not perform any changes of the
> List object. This informs the compiler to allow isEmpty() calls for a
> const list object such as:
> 
> void my_function(const List& list) {
> 	if (!list.isEmpty()) {
> 		....
> 	}
> }
> 
> /Per W
> 
> On Tue, 28 Oct 2003, Devan Lippman wrote:
> 
> 
>>>From the following line of code:
>>  bool empty = aList.isEmpty();
>>I'm getting this error:
>>  passing `const List' as `this' argument of `bool
>>  List::isEmpty()' discards qualifiers
>>
>>isEmpty() is a member function that returns a bool
>>
>>Thank you,
>>Devan Lippman <dli...@co...>
>>(617) 571-3017
>>
>>Using Dev-C++ version: 4.9.8.4
>>
>>Compiler Log:
>>Compiler: Default compiler
>>Building Makefile: "C:\Dev-Cpp\HW6\Makefile.win"
>>Executing  make...
>>make.exe -f "C:\Dev-Cpp\HW6\Makefile.win" all
>>g++.exe -c dlippman-6.cpp -o dlippman-6.o -I"C:/Dev-Cpp/include/c++"
-I"C:/Dev-
>>Cpp/include/c++/mingw32"  -I"C:/Dev-Cpp/include/c++/backward"  -I"C:/Dev-
>>Cpp/include"
>>
>>dlippman-6.cpp: In function `void firstElement(const List&, ListItemType&,
>>   bool&)':
>>dlippman-6.cpp:54: passing `const List' as `this' argument of `bool
>>
>>   List::isEmpty()' discards qualifiers
>>
>>dlippman-6.cpp:56: passing `const List' as `this' argument of `void
>>   List::retrieve(int, ListItemType&, bool&)' discards qualifiers
>>
>>dlippman-6.cpp: In function `void lastElement(const List&, ListItemType&,
>>   bool&)':
>>dlippman-6.cpp:63: passing `const List' as `this' argument of `bool
>>   List::isEmpty()' discards qualifiers
>>
>>dlippman-6.cpp:63: passing `const List' as `this' argument of `int
>>   List::getLength()' discards qualifiers
>>
>>dlippman-6.cpp:63: passing `const List' as `this' argument of `void
>>   List::retrieve(int, ListItemType&, bool&)' discards qualifiers
>>
>>dlippman-6.cpp: In function `void lookupValue(const List&, int, int&,
bool&)':
>>
>>dlippman-6.cpp:75: passing `const List' as `this' argument of `int
>>   List::getLength()' discards qualifiers
>>
>>dlippman-6.cpp:76: passing `const List' as `this' argument of `void
>>   List::retrieve(int, ListItemType&, bool&)' discards qualifiers
>>
>>dlippman-6.cpp: In function `void testList()':
>>
>>dlippman-6.cpp:142: parse error before `{' token
>>
>>dlippman-6.cpp:149: return-statement with a value, in function declared
with a
>>   void return type
>>
>>dlippman-6.cpp:153: parse error at end of input
>>
>>make.exe: *** [dlippman-6.o] Error 1
>>
>>Execution terminated
>>
>>
>>
> 
> 
> 
> 
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