• d-bugmail puremagic.com (41/41) Jan 19 2011 http://d.puremagic.com/issues/show_bug.cgi?id=5462

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=5462

           Summary: std.container.BinaryHeap enforce message + pop
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



A D2 program:

import std.container;
void main() {
    auto h = BinaryHeap!(int[])([]);
    h.removeFront();
}


It throws the exception:
object.Exception ...\dmd\src\phobos\std\container.d(2592): Enforcement failed

In a larger program such error message is bad because it doesn't give a lot of
information. To improve the situation a little I suggest to modify the enforce
at line 2592:

    void removeFront()
    {
        enforce(!empty);

Adding an error message that helps understand what the error is:

enforce(!empty, "Attempt to remove the front of an empty heap");

(The future stack trace on Windows will probably also give the line number 4 of
the user program.)

-------------------------

In code that uses the BinaryHeap I've often used two lines of code like this:

auto item = heap.front();
heap.removeFront();

So I suggest to add to BinaryHeap a handy member function pop() that does both
things:
auto item = heap.pop();

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