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db_include/nodes/value.h

@@ -0,0 +1,61 @@
+/*-------------------------------------------------------------------------
+ *
+ * value.h
+ *	  interface for Value nodes
+ *
+ *
+ * Copyright (c) 2003-2021, PostgreSQL Global Development Group
+ *
+ * src/include/nodes/value.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef VALUE_H
+#define VALUE_H
+
+#include "nodes/nodes.h"
+
+/*----------------------
+ *		Value node
+ *
+ * The same Value struct is used for five node types: T_Integer,
+ * T_Float, T_String, T_BitString, T_Null.
+ *
+ * Integral values are actually represented by a machine integer,
+ * but both floats and strings are represented as strings.
+ * Using T_Float as the node type simply indicates that
+ * the contents of the string look like a valid numeric literal.
+ *
+ * (Before Postgres 7.0, we used a double to represent T_Float,
+ * but that creates loss-of-precision problems when the value is
+ * ultimately destined to be converted to NUMERIC.  Since Value nodes
+ * are only used in the parsing process, not for runtime data, it's
+ * better to use the more general representation.)
+ *
+ * Note that an integer-looking string will get lexed as T_Float if
+ * the value is too large to fit in an 'int'.
+ *
+ * Nulls, of course, don't need the value part at all.
+ *----------------------
+ */
+typedef struct Value
+{
+	NodeTag		type;			/* tag appropriately (eg. T_String) */
+	union ValUnion
+	{
+		int			ival;		/* machine integer */
+		char	   *str;		/* string */
+	}			val;
+} Value;
+
+#define intVal(v)		(((Value *)(v))->val.ival)
+#define floatVal(v)		atof(((Value *)(v))->val.str)
+#define strVal(v)		(((Value *)(v))->val.str)
+
+extern Value *makeInteger(int i);
+extern Value *makeFloat(char *numericStr);
+extern Value *makeString(char *str);
+extern Value *makeBitString(char *str);
+
+#endif							/* VALUE_H */