From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 124940 invoked by alias); 20 Sep 2016 16:36:02 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 124917 invoked by uid 89); 20 Sep 2016 16:36:01 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-5.0 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 20 Sep 2016 16:36:00 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 36B2EC00B6F2 for ; Tue, 20 Sep 2016 16:35:58 +0000 (UTC) Received: from localhost (ovpn-116-66.ams2.redhat.com [10.36.116.66]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u8KGZv3h007149; Tue, 20 Sep 2016 12:35:57 -0400 Date: Tue, 20 Sep 2016 16:41:00 -0000 From: Jonathan Wakely To: Pedro Alves Cc: gdb-patches@sourceware.org Subject: Re: [PATCH] Implement floordiv operator for gdb.Value Message-ID: <20160920163556.GB5736@redhat.com> References: <20160920132633.GA897@redhat.com> <883c76d5-54e9-e8fe-5713-eec2c4010498@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <883c76d5-54e9-e8fe-5713-eec2c4010498@redhat.com> X-Clacks-Overhead: GNU Terry Pratchett User-Agent: Mutt/1.7.0 (2016-08-17) X-SW-Source: 2016-09/txt/msg00229.txt.bz2 On 20/09/16 16:33 +0100, Pedro Alves wrote: >Hi there, > >Thanks! > >On 09/20/2016 02:26 PM, Jonathan Wakely wrote: >> This is my attempt to implement the // operator on gdb.Value objects. >> There is already BINOP_INTDIV which works fine for integral types, but >> for floats I use BINOP_DIV and then call floor() on the result. This >> doesn't support decimal floats though. >> >> Is this a reasonable solution? Is the test sufficient? >> > >See below. > >> @@ -1142,7 +1160,15 @@ valpy_binop_throw (enum valpy_opcode opcode, PyObject *self, PyObject *other) >> } >> >> if (res_val) >> - result = value_to_value_object (res_val); >> + { >> + if (floor_it) >> + { >> + double d = value_as_double (res_val); > >Should be s/double/DOUBLEST, I suppose? OK - if I do that then floor(d) will convert it back to double, unless you #include and using std::floor, so that the overload for long double is visible (in C++ names like floor are overloaded so you don't need to use floorf/floor/floorl according to the type). >> diff --git a/gdb/testsuite/gdb.python/py-value.exp b/gdb/testsuite/gdb.python/py-value.exp >> index 57a9ba1..81837e9 100644 >> --- a/gdb/testsuite/gdb.python/py-value.exp >> +++ b/gdb/testsuite/gdb.python/py-value.exp >> @@ -87,6 +87,8 @@ proc test_value_numeric_ops {} { >> gdb_test "python print ('result = ' + str(f/g))" " = 0.5" "divide two double values" >> gdb_test "python print ('result = ' + str(i%j))" " = 1" "take remainder of two integer values" >> # Remainder of float is implemented in Python but not in GDB's value system. >> + gdb_test "python print ('result = ' + str(i//j))" " = 2" "floor-divide two integer values" >> + gdb_test "python print ('result = ' + str(f//g))" " = 0" "floor-divide two double values" > >Is the "two double values" test returning an integer somehow? > >I ask because IIUC, regardless of Python version, a floor-divide >involving a float should result in a float, while a floor-divide of >integers should result in an integer. And that's what the patch looks >like should end up with. So I was expecting to see "0.0" in >the "two double values" case: > > (gdb) python print (5.0//6.0) > 0.0 > (gdb) python print (5//6) > 0 This seems to be an existing property of gdb.Value, as even using the normal division operator (and without my patch) I see floats printed without a decimal part when they are an integer value: (gdb) python print (gdb.Value(5.0)/5.0) 1 (gdb) python print (5.0/5.0) 1.0 >I think it'd be good to test with negative numbers too, to make >sure that we round (and keep rounding) toward the same >direction Python rounds: > > (gdb) python print (8.0//-3) > -3.0 > (gdb) python print (8//-3) > -3 > (gdb) print 8/-3 > $1 = -2 Good point, I'll do that.