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From: Nathan Bossart <nathandbossart@gmail.com>
To: Joseph Koshakow <koshy44@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Andres Freund <andres@anarazel.de>
Subject: Re: Remove dependence on integer wrapping
Date: Mon, 15 Jul 2024 10:31:08 -0500
Message-ID: <ZpVAvLbtUPnK1JKe@nathan> (raw)
In-Reply-To: <CAAvxfHdX-t03LvxROxbyodBrtzBzZQEKdKB0FCpEr+p1JnFxsA@mail.gmail.com>
References: <ZmZbXK1CNMbkty0W@nathan>
	<618777.1717984674@sss.pgh.pa.us>
	<31ad2cd1-db94-bdb3-f91a-65ffdb4bef95@gmail.com>
	<CAAvxfHfqJca-WGvWJQ3ZAtt2po=mkQzU8r9Qjzom4YqxQi84oA@mail.gmail.com>
	<CAAvxfHdhEz4eF7z1wNn_4C4Gkt+e-h7OjzKUJXt7CE+CvubqcQ@mail.gmail.com>
	<CAAvxfHdze21+UZPWo7ePfH19-9hvXe_9SEZk4HABPHuzaUitRQ@mail.gmail.com>
	<CAAvxfHd22ujbY6uTraE+ZSTUN0xX0G-=NZcr0YnKSQuXthcM+g@mail.gmail.com>
	<CAAvxfHcDQEziyQ-ehv0Bg05OovGPGO95VoO7-DyxJx6Tkq85vA@mail.gmail.com>
	<ZpFeopUrhdB5GgNN@nathan>
	<CAAvxfHdX-t03LvxROxbyodBrtzBzZQEKdKB0FCpEr+p1JnFxsA@mail.gmail.com>

I took a closer look at 0002.

+    if (unlikely(isinf(f) || isnan(f)))
+        ereport(ERROR,
+                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+                 errmsg("invalid float value")));
+
+    fresult = rint(f * c);

+    if (unlikely(f == 0.0))
+        ereport(ERROR,
+                (errcode(ERRCODE_DIVISION_BY_ZERO),
+                 errmsg("division by zero")));
+    if (unlikely(isinf(f) || isnan(f)))
+        ereport(ERROR,
+                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+                 errmsg("invalid float value")));
+
+    fresult = rint(c / f);

I'm curious why you aren't using float8_mul/float8_div here, i.e.,

	fresult = rint(float8_mul((float8) c, f));
	fresult = rint(float8_div((float8) c, f));

nitpick: I'd name the functions something like "cash_mul_float8" and
"cash_div_float8".  Perhaps we could also add functions like
"cash_mul_int64" and "cash_sub_int64" so that we don't need several copies
of the same "money out of range" ERROR.

-- 
nathan





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  Cc: nathandbossart@gmail.com, koshy44@gmail.com, exclusion@gmail.com, tgl@sss.pgh.pa.us, pgsql-hackers@lists.postgresql.org, andres@anarazel.de
  Subject: Re: Remove dependence on integer wrapping
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