Author: Richard Pijl
Date: 04:23:28 05/28/04
Go up one level in this thread
On May 28, 2004 at 05:54:43, Uri Blass wrote:
>On May 27, 2004 at 20:11:52, Filip Tvrzsky wrote:
>
>>On May 27, 2004 at 19:05:42, Uri Blass wrote:
>>
>>>On May 27, 2004 at 18:41:59, Randall Shane wrote:
>>>
>>>>On May 27, 2004 at 18:10:47, Uri Blass wrote:
>>>><snippage>
>>>>>
>>>>>I do not get the same move twice when I have
>>>>>printf("%s ",move_str(0));
>>>>>printf("%s ",move_str(1));
>>>>>
>>>>>I thought that
>>>>>printf("%s %s ",move_str(0),move_str(1));
>>>>>should be exactly the same instruction.
>>>>>
>>>>>I understand now that it is not and the second printf does not print move_str(1)
>>>>>immediatly after it calculates it but calculates also move_str(0) and change the
>>>>>value of move_str(1) by doing it.
>>>>>
>>>>>I think that it is a bug in the language or in the compiler because it is clear
>>>>>that the programmer mean the same in both cases.
>>>>>
>>>>>
>>>>>correct compiler can solve the problem by translating
>>>>>
>>>>>printf("%s %s ",move_str(0),move_str(1));
>>>>>to
>>>>>printf("%s ",move_str(0));
>>>>>printf("%s ",move_str(1));
>>>>>
>>>>>I see no logical reason not to translate it in that way from human point of
>>>>>view.
>>>>
>>>>Ah, but how is the compiler supposed to know that you didn't mean to overwrite
>>>>the array, which is defined internal to your move_str routine?
>>> Without
>>>>extensive and deep analysis of the routines, it can't make that assumption.
>>>
>>>
>>>I think it can make this assumption.
>>>I see no reason to write one printf of 2 strings and to mean different thing
>>>than the thing that is done by 2 printf.
>>>
>>>It is a confusing code.
>>
>>Uri, I am sorry, but this is really YOUR fault, not compiler fault. I am also
>>little bit suprised at your complaints about compiler behaviour knowing your
>>strictly logical style of thinking. Because when you read language specification
>>and think thoroughly about it then you should realize that compiler does exactly
>>what is supposed to do and not what it could assume to be your wish. And thank
>>God for it! Because I am sick of software which knows better than me what I
>>want.
>>Filip
>
>In that case it is a mistake in defining the language.
>
>I did not read language specification and I simply generalized based on previous
>experience.
>
>I also think that the compiler should at least give a warning in that case
>because I guess that I am not the first person and not the last person to do
>that kind of mistake.
If you really think that is the case you should probably use a language like
Pascal or Modula-II instead. Or perhaps Java? Those languages prevent a lot of
these mistakes by not allowing the constructions that cause them.
Point is that C gives you a lot of possibilities in fiddling with data and data
access. That gives great flexibility, but asks of the programmer to take care
when using those tricks.
move_str() returns a pointer. And the memory location will contain the stuff you
have asked for. In principle you don't care where it is located. The
disadvantage is that you should be aware of the limited validity of this
content. In this case until the next call to move_str().
If you do not want this restriction, you have to rewrite move_str by either
supplying a memory location that the calling function controls, or by
dynamically allocation memory to store the string (slow!!) where you should not
forget to free that memory again when you no longer need it (i.e. after the
printf).
>I guess that in big majority of the cases that programmers write printf("%s %s
>",a,b);
>they mean printf("%s ",a); orintf(" %s ",b);
printf is a function. Printf is a special function because it allows an
unspecified number of parameters, and handles them correctly.
Before a function is called, all of its arguments are evaluated. If those
arguments are functions, the functions will be called and the result is used as
an argument to (in this case) printf.
You can define your own functions with unspecified number of parameters. Do you
want the compiler to decide that
urifunction(a,b,b);
is equal to
urifunction(a1,b);
urifunction(a2,b);
?
Richard.
>
>If the expressions are not the same the compiler should at least warn the
>programmer about it.
>
>Uri
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