Got most of the new memory architecture roughed out.

src/c/payloads/string.h

@@ -0,0 +1,42 @@
+/**
+ *  payloads/string.h
+ *
+ *  A string cell.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_payloads_string_h
+#define __psse_payloads_string_h
+/*
+ * wide characters
+ */
+#include <wchar.h>
+#include <wctype.h>
+
+#include "memory/pointer.h"
+
+
+/**
+ * @brief Tag for string of characters, organised as a linked list.
+ */
+#define STRINGTAG   "STR"
+
+/**
+ * @brief payload of a string cell. 
+ *
+ * At least at first, only one UTF character will be stored in each cell. At 
+ * present the payload of a symbol or keyword cell is identical
+ * to the payload of a string cell.
+ */
+struct string_payload {
+    /** the actual character stored in this cell */
+    wint_t character;
+    /** a hash of the string value, computed at store time. */
+    uint32_t hash;
+    /** the remainder of the string following this character. */
+    struct cons_pointer cdr;
+};
+
+#endif