From 4b630d4f278d234976575f572d5ff8b86c7b1bbe Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Mon, 4 Dec 2023 12:27:13 -0800
Subject: [PATCH] Added cast from half to real [skip ci]

---
 sql/vector--0.5.1--0.6.0.sql |  6 ++++++
 sql/vector.sql               |  6 ++++++
 src/half.c                   | 13 +++++++++++++
 test/expected/half.out       | 12 ++++++++++++
 test/sql/half.sql            |  3 +++
 5 files changed, 40 insertions(+)

diff --git a/sql/vector--0.5.1--0.6.0.sql b/sql/vector--0.5.1--0.6.0.sql
index 61348fa..5687c0a 100644
--- a/sql/vector--0.5.1--0.6.0.sql
+++ b/sql/vector--0.5.1--0.6.0.sql
@@ -46,6 +46,9 @@ CREATE FUNCTION half_negative_inner_product(half[], half[]) RETURNS float8
 CREATE FUNCTION float4_to_half(real, integer, boolean) RETURNS half
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION half_to_float4(half, integer, boolean) RETURNS real
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION integer_to_half(integer, integer, boolean) RETURNS half
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
@@ -55,6 +58,9 @@ CREATE FUNCTION numeric_to_half(numeric, integer, boolean) RETURNS half
 CREATE CAST (real AS half)
 	WITH FUNCTION float4_to_half(real, integer, boolean) AS IMPLICIT;
 
+CREATE CAST (half AS real)
+	WITH FUNCTION half_to_float4(half, integer, boolean) AS IMPLICIT;
+
 CREATE CAST (integer AS half)
 	WITH FUNCTION integer_to_half(integer, integer, boolean) AS IMPLICIT;
 
diff --git a/sql/vector.sql b/sql/vector.sql
index c86d6d9..bdecf37 100644
--- a/sql/vector.sql
+++ b/sql/vector.sql
@@ -344,6 +344,9 @@ CREATE FUNCTION half_negative_inner_product(half[], half[]) RETURNS float8
 CREATE FUNCTION float4_to_half(real, integer, boolean) RETURNS half
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION half_to_float4(half, integer, boolean) RETURNS real
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION integer_to_half(integer, integer, boolean) RETURNS half
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
@@ -355,6 +358,9 @@ CREATE FUNCTION numeric_to_half(numeric, integer, boolean) RETURNS half
 CREATE CAST (real AS half)
 	WITH FUNCTION float4_to_half(real, integer, boolean) AS IMPLICIT;
 
+CREATE CAST (half AS real)
+	WITH FUNCTION half_to_float4(half, integer, boolean) AS IMPLICIT;
+
 CREATE CAST (integer AS half)
 	WITH FUNCTION integer_to_half(integer, integer, boolean) AS IMPLICIT;
 
diff --git a/src/half.c b/src/half.c
index 96a3100..3991ab0 100644
--- a/src/half.c
+++ b/src/half.c
@@ -439,6 +439,19 @@ float4_to_half(PG_FUNCTION_ARGS)
 	PG_RETURN_HALF(h);
 }
 
+/*
+ * Convert half to float4
+ */
+PGDLLEXPORT PG_FUNCTION_INFO_V1(half_to_float4);
+Datum
+half_to_float4(PG_FUNCTION_ARGS)
+{
+	half		h = PG_GETARG_HALF(0);
+	float		f = HalfToFloat4(h);
+
+	PG_RETURN_FLOAT4(f);
+}
+
 /*
  * Get the L2 distance between half arrays
  */
diff --git a/test/expected/half.out b/test/expected/half.out
index 5e54327..ae1e391 100644
--- a/test/expected/half.out
+++ b/test/expected/half.out
@@ -76,6 +76,18 @@ SELECT 'Infinity'::real::half;
  Infinity
 (1 row)
 
+SELECT '1.5'::half::real;
+ float4 
+--------
+    1.5
+(1 row)
+
+SELECT '{1.5}'::half[]::real[];
+ float4 
+--------
+ {1.5}
+(1 row)
+
 SELECT l2_distance('{0,0}'::half[], '{3,4}'::half[]);
  l2_distance 
 -------------
diff --git a/test/sql/half.sql b/test/sql/half.sql
index 3db34ba..166cd23 100644
--- a/test/sql/half.sql
+++ b/test/sql/half.sql
@@ -17,6 +17,9 @@ SELECT '65505'::integer::half;
 SELECT 'NaN'::real::half;
 SELECT 'Infinity'::real::half;
 
+SELECT '1.5'::half::real;
+SELECT '{1.5}'::half[]::real[];
+
 SELECT l2_distance('{0,0}'::half[], '{3,4}'::half[]);
 SELECT l2_distance('{0,0}'::half[], '{0,1}'::half[]);
 SELECT l2_distance('{1,2}'::half[], '{3}'::half[]);