Added work on making namespaces threadsafe.

src/c/ops/truth.c

@@ -0,0 +1,94 @@
+/**
+ *  ops/truth.c
+ *
+ *  Post Scarcity Software Environment: nil? true? not.
+ *
+ *  Functions associated with truthiness.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+/**
+ * @brief true if `p` points to `nil`, else false.
+ *
+ * Note that every node has its own copy of `t` and `nil`, and each instance of 
+ * each is considered equivalent. So we don't check the node when considering
+ * whether `nil` really is `nil`, or `t` really is `t`.
+ * 
+ * @param p a pointer
+ * @return true if `p` points to `nil`.
+ * @return false otherwise.
+ */
+bool nilp( struct pso_pointer p) {
+    return (p.page == 0 && p.offset = 0);
+}
+
+/**
+ * @brief Return `true` if `p` points to `nil`, else `false`.
+ * 
+ * @param p a pointer
+ * @return true  if `p` points to `nil`;
+ * @return false  otherwise.
+ */
+bool not( struct pso_pointer p) {
+    return !nilp( p);
+}
+
+/**
+ * @brief `true` if `p` points to `t`, else `false`.
+ *
+ * Note that every node has its own copy of `t` and `nil`, and each instance of 
+ * each is considered equivalent. So we don't check the node when considering
+ * whether `nil` really is `nil`, or `t` really is `t`.
+ * 
+ * @param p a pointer
+ * @return true if `p` points to `t`.
+ * @return false otherwise.
+ */
+bool truep( struct pso_pointer p) {
+    return (p.page == 0 && p.offset = 1);
+}
+
+/**
+ * @brief return `t` if the first argument in this frame is `nil`, else `t`.
+ * 
+ * @param frame The current stack frame;
+ * @param frame_pointer A pointer to the current stack frame;
+ * @param env the evaluation environment.
+ * @return `t` if the first argument in this frame is `nil`, else `t`
+ */
+pso_pointer lisp_nilp( struct stack_frame *frame,
+                                  struct pso_pointer frame_pointer,
+                                  struct pso_pointer env ){
+    return (nilp(frame->arg[0]) ? t : nil);
+}
+
+/**
+ * @brief return `t` if the first argument in this frame is `t`, else `nil`.
+ * 
+ * @param frame The current stack frame;
+ * @param frame_pointer A pointer to the current stack frame;
+ * @param env the evaluation environment.
+ * @return `t` if the first argument in this frame is `t`, else `nil`.
+ */
+pso_pointer lisp_truep( struct stack_frame *frame,
+                                  struct pso_pointer frame_pointer,
+                                  struct pso_pointer env ){
+    return (truep(frame->arg[0]) ? t : nil);
+}
+
+/**
+ * @brief return `t` if the first argument in this frame is not `nil`, else 
+ * `t`.
+ * 
+ * @param frame The current stack frame;
+ * @param frame_pointer A pointer to the current stack frame;
+ * @param env the evaluation environment.
+ * @return `t` if the first argument in this frame is not `nil`, else `t`.
+ */
+pso_pointer lisp_not( struct stack_frame *frame,
+                                  struct pso_pointer frame_pointer,
+                                  struct pso_pointer env ){
+    return (not(frame->arg[0]) ? t : nil);
+}