Parsing isn't this hard?

2023-02-02 08:32:45 -08:00
parent 9356e5394b
commit ebae69c391
2 changed files with 323 additions and 95 deletions
@@ -47,3 +47,158 @@ typedef struct list_node* JoyList;
 	/*gmp_printf("%Zd = %Zx\n", pi, pi);*/
 	/*mpz_mul(pi, pi, pi);*/
 	/*gmp_printf("%Zd = %Zx\n", pi, pi);*/
+'
+
+
+
+
+
+
+
+
+/*=======================================================*/
+struct list_node*
+text_to_expression(char *text)
+{
+	char *rest;
+	ptrdiff_t diff;
+	struct list_node *thing;
+	struct list_node *result;
+	struct list_node *tail = NULL;
+	struct list_node *stack[128];
+	int s = 0; /* stack pointer */
+
+	/* NULL string input? */
+	if (NULL == text) {
+		return EMPTY_LIST;
+	}
+
+	text = trim_leading_blanks(text);
+
+	/* All blanks? */
+	if (NULL == text) {
+		return EMPTY_LIST;
+	}
+
+	/* Look for blanks or brackets. */
+	rest = strpbrk(text, " []");
+	/*
+	rest now points to a space or '[' or ']' after a term,
+	-or- it is NULL if the rest of the string is a single term
+	with no spaces nor brackets.  If that's the case then we're
+	done, and we can just return a list with one symbol in it.
+	*/
+	if (NULL == rest) {
+		return make_symbol_node(text, strlen(text));
+	}
+
+	/* How many chars have we got? */
+	diff = rest - text;
+
+	if (diff) {
+		thing = make_symbol_node(text, diff);
+		if (tail) {
+			tail->tail = thing;
+		} else {
+			/* There is no head now, so this must be the first
+			   result, the head that we will eventually return. */
+			result = thing;
+		}
+		tail = thing;
+
+	} else if ('[' == rest[0]) {
+		rest++;
+		/* We need to parse a sub-list. */
+		if (tail) {
+			/* We have already parsed some terms, set them aside. */
+			stack[s++] = tail;
+			stack[s++] = result;
+			tail = (struct list_node *)NULL;
+		} else {
+			/*
+			This is going to be our first term when we're done parsing it.
+			Do nothing, empty stack will signal it.
+			*/
+			
+		}
+	} else if (']' == rest[0]) {
+		rest++;
+		if (s) {
+			/* We have a tail on the stack. */
+			thing = result;
+			result = stack[--s];
+			tail = stack[--s];
+			tail->tail = thing;
+		} else {
+			/* This list must have been the first thing in the expr. */
+			printf("wtf");
+			exit(1);
+		}
+	} else {
+		
+	}
+
+	result = make_symbol_node(text, diff);
+	
+	/*
+	This is the head of the list we are eventually going to return,
+	so we assign it to the result
+	We are going to be adding things to the tail of this list, so
+	we'll need to keep track of that
+	*/
+	tail = result;
+	
+	/*
+	Now we want to 
+	*/
+	while (NULL != rest) {
+	
+
+			if (head) {
+				head->tail = current_list_node;
+			} else {
+				/* There is no head now, so this must be the first
+				   result, the head that we will eventually return. */
+				result = current_list_node;
+			}
+			head = current_list_node;
+		}
+
+		/* The next char is a space or '[' or ']'. */
+		if ('[' == rest[0]) {
+			if (head) {
+				stack[s++] = head;
+				head = (struct list_node *)NULL;
+			}
+			/*printf("%c\n", rest[0]);*/
+		}
+
+		if (']' == rest[0]) {
+			current_list_node = make_list_node(stack[s--]);
+			if (head) {
+				head->tail = current_list_node;
+			} else {
+				/* There is no head now, so this must be the first
+				   result, the head that we will eventually return. */
+				result = current_list_node;
+			}
+			head = current_list_node;
+			/*printf("%c\n", rest[0]);*/
+		}
+
+		text = trim_leading_blanks(++rest);
+
+		/* calling strpbrk on NULL caused segfault! */
+		rest = (NULL != text) ? strpbrk(text, " []") : text;
+	}
+	if (text) {
+		current_list_node = make_symbol_node(text, strlen(text));
+		if (head) {
+			head->tail = current_list_node;
+		} else {
+			result = current_list_node;
+		}
+	}
+	return result;
+}
+'