Add range type over units: unitrange.

Suggested by Gavin Wahl, thanks!

Close #22.

Author: df7cb

Diff for: NEWS.md

@@ -11,6 +11,7 @@
 * Support Infinity and NaN.
 * Add strict comparison operators that error out when dimensions of arguments
   do not match: << <<= == <<>> >>= >>.
+* Add range type over units: unitrange.
 
 6.0: Mar 7, 2018
 ----------------

Diff for: debian/changelog

@@ -11,6 +11,7 @@ postgresql-unit (7.0-1) UNRELEASED; urgency=medium
   * Support Infinity and NaN.
   * Add strict comparison operators that error out when dimensions of
     arguments do not match: << <<= == <<>> >>= >>.
+  * Add range type over units: unitrange.
 
  -- Christoph Berg <[email protected]>  Sun, 08 Jul 2018 21:46:17 +0200
 

Diff for: expected/compare.out

@@ -232,3 +232,28 @@ SELECT '1 m'::unit >> '1 m'::unit;
 
 SELECT '1 m'::unit >> '1 A'::unit;
 ERROR:  dimension mismatch in "strict comparison" operation: "1 m", "1 A"
+-- test range type
+SELECT 'empty'::unitrange;
+ unitrange 
+-----------
+ empty
+(1 row)
+
+SELECT '(1 m, 2 m)'::unitrange;
+   unitrange   
+---------------
+ ("1 m","2 m")
+(1 row)
+
+SELECT '(1 m, 2 A)'::unitrange;
+ERROR:  dimension mismatch in "strict comparison" operation: "1 m", "2 A"
+LINE 1: SELECT '(1 m, 2 A)'::unitrange;
+               ^
+SELECT unit_diff('1 A', '2 A');
+ unit_diff 
+-----------
+        -1
+(1 row)
+
+SELECT unit_diff('1 A', '2 K');
+ERROR:  dimension mismatch in "-" operation: "1 A", "2 K"

Diff for: sql/compare.sql

@@ -51,3 +51,10 @@ SELECT '1 m'::unit >>= '1 m'::unit;
 SELECT '1 m'::unit >>= '1 A'::unit;
 SELECT '1 m'::unit >> '1 m'::unit;
 SELECT '1 m'::unit >> '1 A'::unit;
+
+-- test range type
+SELECT 'empty'::unitrange;
+SELECT '(1 m, 2 m)'::unitrange;
+SELECT '(1 m, 2 A)'::unitrange;
+SELECT unit_diff('1 A', '2 A');
+SELECT unit_diff('1 A', '2 K');

Diff for: unit--6--7.sql.in

@@ -95,5 +95,20 @@ CREATE OPERATOR CLASS unit_strict_ops
 		OPERATOR 5 >> ,
 		FUNCTION 1 unit_strict_cmp(unit, unit);
 
+-- range type
+
+CREATE FUNCTION unit_diff(unit, unit)
+	RETURNS float8
+	AS '$libdir/unit'
+	LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION unit_diff IS 'returns difference of two units as float8 for use in the unitrange type';
+
+CREATE TYPE unitrange AS RANGE (
+	SUBTYPE = unit,
+	SUBTYPE_OPCLASS = unit_strict_ops,
+	SUBTYPE_DIFF = unit_diff
+);
+
 -- load prefixes and units tables
 SELECT unit_load();

Diff for: unit--7.sql.in

@@ -576,6 +576,21 @@ CREATE OPERATOR CLASS unit_strict_ops
 		OPERATOR 5 >> ,
 		FUNCTION 1 unit_strict_cmp(unit, unit);
 
+-- range type
+
+CREATE FUNCTION unit_diff(unit, unit)
+	RETURNS float8
+	AS '$libdir/unit'
+	LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION unit_diff IS 'returns difference of two units as float8 for use in the unitrange type';
+
+CREATE TYPE unitrange AS RANGE (
+	SUBTYPE = unit,
+	SUBTYPE_OPCLASS = unit_strict_ops,
+	SUBTYPE_DIFF = unit_diff
+);
+
 -- aggregates
 
 CREATE AGGREGATE sum(unit)

Diff for: unit.c

@@ -728,6 +728,19 @@ unit_round(PG_FUNCTION_ARGS)
 	PG_RETURN_POINTER(result);
 }
 
+PG_FUNCTION_INFO_V1(unit_diff);
+
+Datum
+unit_diff(PG_FUNCTION_ARGS)
+{
+	Unit	*a = (Unit *) PG_GETARG_POINTER(0);
+	Unit	*b = (Unit *) PG_GETARG_POINTER(1);
+	Unit	 result;
+
+	unit_sub_internal(a, b, &result);
+	PG_RETURN_FLOAT8(result.value);
+}
+
 /* operators */
 
 PG_FUNCTION_INFO_V1(unit_add);