[Issue 3847] New: To avoid a C code bug

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3847

           Summary: To avoid a C code bug
           Product: D
           Version: 2.040
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2010-02-23 18:11:52 PST ---
What does this D2 program print, and why?


import std.stdio;

bool thirdElementIsThree(int[] a) {
    return a.length >= 3 & a[2] == 3;
}

void main() {
    int[][] tests = [[6, 5, 4, 3, 2, 1],
                     [1, 2],
                     [1, 2, 3],
                     [1, 2, 3, 4 ],
                     [1]];
    int n = 0;

    try {
        int i = 0;
        while (true) {
            if (thirdElementIsThree(tests[i++]))
                n++;
        }
    } catch(Error e) {
        // No more tests to process
    }

    writeln(n); // prints?
}



Using 'and' and 'or' instead of && and || helps reduce some possible programmer
mistakes, because the programmer may write & or | and the compiler may not
catch the mistake. Using those keyword (as in Python and many other languages)
avoids such mistakes, and C programmer will not be confused by this change
because the || and && becomes deprecated, as the 'l' suffix for numbers. 'and'
and 'or' are also quite less cryptic than && and || symbols.

&& and || can be kept to keep C compatibility, but their usage can be
discouraged in new normal D2 code.

In real code it happens to write a & where you want to write &&, this is not an
uncommon bug.

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