Floating point computation issue?

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ejlis...@yahoo.fr

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Jun 7, 2012, 12:58:42 PM6/7/12
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Hi all,

Does anyone know why JSDB (win version, did not check others) and SQLite
do not get the same result in the following situation?

---

R:\>jsdb.exe
js>var db = new SQLite();
js>db.exec("select 999901/10.0", function(r){println(r.toString())});
999901/10.0=99990.1000000001
true
js>exit


R:\>SQLite.exe NUL "select 999901/10.0;"
99990.1

---

Regards,
Etienne


P.S. Keep up the good work Shanti!

Jason S

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Jun 8, 2012, 9:50:47 PM6/8/12
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R:\>jsdb.exe

js>var db = new SQLite();
js>db.exec("select 999901/10.0", function(r){println(r.toString())});
999901/10.0=99990.1000000001
true
js>exit


R:\>SQLite.exe NUL "select 999901/10.0;"
99990.1


The former goes through Javascript (the call of r.toString()); the latter does not.

Shanti Rao

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Jun 8, 2012, 11:42:54 PM6/8/12
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That's what I thought at first, but it actually turned out to be quite subtle. A 32-bit float with a rounding error is promoted to double by the compiler in a call to sqlite3_snprintf(). The fix wouls be to change how JSDB converts SQLite values to text in sqlite_exec().

Dies anyone else need thus fixed?

Shanti

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