[HACKERS] [PATCH 1/3] Implement tau() function

[Asbjørn Sloth Tønnesen]

Signed-off-by: Asbjørn Sloth Tønnesen <asbj...@asbjorn.it>
---
 doc/src/sgml/func.sgml        | 13 +++++++++++++
 src/backend/utils/adt/float.c | 17 +++++++++++++++--
 src/include/catalog/pg_proc.h |  2 ++
 src/include/utils/builtins.h  |  1 +
 4 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 551576a..2b48123 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -878,6 +878,19 @@
       <row>
        <entry>
         <indexterm>
+         <primary>tau</primary>
+        </indexterm>
+        <literal><function>tau()</function></literal>
+       </entry>
+       <entry><type>dp</type></entry>
+       <entry><quote>&tau;</quote> constant</entry>
+       <entry><literal>tau()</literal></entry>
+       <entry><literal>6.28318530717959</literal></entry>
+      </row>
+
+      <row>
+       <entry>
+        <indexterm>
          <primary>trunc</primary>
         </indexterm>
         <literal><function>trunc(<type>dp</type> or 
<type>numeric</type>)</function></literal>
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 41b3eaa..1278053 100644
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -26,9 +26,12 @@
 #include "utils/sortsupport.h"
 
 
+#ifndef M_TAU
+#define M_TAU 6.28318530717958647693
+#endif
+
 #ifndef M_PI
-/* from my RH5.2 gcc math.h file - thomas 2000-04-03 */
-#define M_PI 3.14159265358979323846
+#define M_PI (M_TAU / 2.0)
 #endif
 
 /* Visual C++ etc lacks NAN, and won't accept 0.0/0.0.  NAN definition from
@@ -1716,6 +1719,16 @@ dpi(PG_FUNCTION_ARGS)
 
 
 /*
+ *             dtau                            - returns the constant Tau
+ */
+Datum
+dtau(PG_FUNCTION_ARGS)
+{
+       PG_RETURN_FLOAT8(M_TAU);
+}
+
+
+/*
  *             radians         - returns radians converted from degrees
  */
 Datum
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 0b6105b..4148bed 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -1825,6 +1825,8 @@ DATA(insert OID = 1609 (  radians                 PGNSP 
PGUID 12 1 0 0 0 f f f f t f i 1 0 701
 DESCR("degrees to radians");
 DATA(insert OID = 1610 (  pi                           PGNSP PGUID 12 1 0 0 0 
f f f f t f i 0 0 701 "" _null_ _null_ _null_ _null_ dpi _null_ _null_ _null_ 
));
 DESCR("PI");
+DATA(insert OID = 1611 (  tau                          PGNSP PGUID 12 1 0 0 0 
f f f f t f i 0 0 701 "" _null_ _null_ _null_ _null_ dtau _null_ _null_ _null_ 
));
+DESCR("Tau");
 
 DATA(insert OID = 1618 (  interval_mul         PGNSP PGUID 12 1 0 0 0 f f f f 
t f i 2 0 1186 "1186 701" _null_ _null_ _null_ _null_ interval_mul _null_ 
_null_ _null_ ));
 
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index bbb5d39..0258a64 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -408,6 +408,7 @@ extern Datum dsin(PG_FUNCTION_ARGS);
 extern Datum dtan(PG_FUNCTION_ARGS);
 extern Datum degrees(PG_FUNCTION_ARGS);
 extern Datum dpi(PG_FUNCTION_ARGS);
+extern Datum dtau(PG_FUNCTION_ARGS);
 extern Datum radians(PG_FUNCTION_ARGS);
 extern Datum drandom(PG_FUNCTION_ARGS);
 extern Datum setseed(PG_FUNCTION_ARGS);
-- 
2.0.0



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