1 files changed, 80 insertions, 29 deletions

diff --git a/dc/stack.c b/dc/stack.c
index 1d8a9bf..49422df 100644
--- a/dc/stack.c
+++ b/dc/stack.c
@@ -1,11 +1,12 @@
 /* 
  * implement stack functions for dc
  *
- * Copyright (C) 1994, 1997, 1998 Free Software Foundation, Inc.
+ * Copyright (C) 1994, 1997, 1998, 2000, 2005, 2006, 2008, 2012, 2016
+ * Free Software Foundation, Inc.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2, or (at your option)
+ * the Free Software Foundation; either version 3, or (at your option)
  * any later version.
  *
  * This program is distributed in the hope that it will be useful,
@@ -14,12 +15,8 @@
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
- * along with this program; if not, you can either send email to this
- * program's author (see below) or write to:
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
- *    The Free Software Foundation, Inc.
- *    59 Temple Place, Suite 330
- *    Boston, MA 02111 USA
  */
 
 /* This module is the only one that knows what stacks (both the
@@ -41,7 +38,7 @@
 #define Empty_Stack	fprintf(stderr, "%s: stack empty\n", progname)
 
 
-/* simple linked-list implementaion suffices: */
+/* simple linked-list implementation suffices: */
 struct dc_list {
 	dc_data value;
 	struct dc_array *array;	/* opaque */
@@ -53,7 +50,8 @@ typedef struct dc_list dc_list;
 static dc_list *dc_stack=NULL;
 
 /* the named register stacks */
-static dc_list *dc_register[DC_REGCOUNT];
+typedef dc_list *dc_listp;
+static dc_listp dc_register[DC_REGCOUNT];
 
 
 /* allocate a new dc_list item */
@@ -86,7 +84,7 @@ dc_binop DC_DECLARG((op, kscale))
 	dc_data b;
 	dc_data r;
 
-	if (!dc_stack || !dc_stack->link){
+	if (dc_stack == NULL  ||  dc_stack->link == NULL){
 		Empty_Stack;
 		return;
 	}
@@ -126,7 +124,7 @@ dc_binop2 DC_DECLARG((op, kscale))
 	dc_data r1;
 	dc_data r2;
 
-	if (!dc_stack || !dc_stack->link){
+	if (dc_stack == NULL  ||  dc_stack->link == NULL){
 		Empty_Stack;
 		return;
 	}
@@ -164,7 +162,7 @@ dc_cmpop DC_DECLVOID()
 	dc_data a;
 	dc_data b;
 
-	if (!dc_stack || !dc_stack->link){
+	if (dc_stack == NULL  ||  dc_stack->link == NULL){
 		Empty_Stack;
 		return 0;
 	}
@@ -198,7 +196,9 @@ dc_triop DC_DECLARG((op, kscale))
 	dc_data c;
 	dc_data r;
 
-	if (!dc_stack || !dc_stack->link || !dc_stack->link->link){
+	if (dc_stack == NULL
+			|| dc_stack->link == NULL
+			|| dc_stack->link->link == NULL){
 		Empty_Stack;
 		return;
 	}
@@ -244,7 +244,7 @@ dc_clear_stack DC_DECLVOID()
 	dc_list *n;
 	dc_list *t;
 
-	for (n=dc_stack; n; n=t){
+	for (n=dc_stack; n!=NULL; n=t){
 		t = n->link;
 		if (n->value.dc_type == DC_NUMBER)
 			dc_free_num(&n->value.v.number);
@@ -297,7 +297,7 @@ int
 dc_top_of_stack DC_DECLARG((result))
 	dc_data *result DC_DECLEND
 {
-	if (!dc_stack){
+	if (dc_stack == NULL){
 		Empty_Stack;
 		return DC_FAIL;
 	}
@@ -308,9 +308,10 @@ dc_top_of_stack DC_DECLARG((result))
 	return DC_SUCCESS;
 }
 
-/* set *result to a dup of the value on the top of the named register stack */
+/* set *result to a dup of the value on the top of the named register stack,
+ * or 0 (zero) if the stack is empty */
 /*
- * DC_FAIL is returned if the named stack is empty (and *result unchanged),
+ * DC_FAIL is returned if an internal bug is detected
  * DC_SUCCESS is returned otherwise
  */
 int
@@ -322,12 +323,15 @@ dc_register_get DC_DECLARG((regid, result))
 
 	regid = regmap(regid);
 	r = dc_register[regid];
-	if ( ! r ){
-		fprintf(stderr, "%s: register ", progname);
-		dc_show_id(stderr, regid, " is empty\n");
+	if (r==NULL){
+		*result = dc_int2data(0);
+	}else if (r->value.dc_type==DC_UNINITIALIZED){
+		fprintf(stderr, "%s: BUG: register ", progname);
+		dc_show_id(stderr, regid, " exists but is uninitialized?\n");
 		return DC_FAIL;
+	}else{
+		*result = dc_dup(r->value);
 	}
-	*result = dc_dup(r->value);
 	return DC_SUCCESS;
 }
 
@@ -344,7 +348,7 @@ dc_register_set DC_DECLARG((regid, value))
 
 	regid = regmap(regid);
 	r = dc_register[regid];
-	if ( ! r )
+	if (r == NULL)
 		dc_register[regid] = dc_alloc();
 	else if (r->value.dc_type == DC_NUMBER)
 		dc_free_num(&r->value.v.number);
@@ -369,7 +373,7 @@ dc_pop DC_DECLARG((result))
 	dc_list *r;
 
 	r = dc_stack;
-	if (!r){
+	if (r==NULL || r->value.dc_type==DC_UNINITIALIZED){
 		Empty_Stack;
 		return DC_FAIL;
 	}
@@ -396,7 +400,7 @@ dc_register_pop DC_DECLARG((stackid, result))
 
 	stackid = regmap(stackid);
 	r = dc_register[stackid];
-	if (!r){
+	if (r==NULL || r->value.dc_type==DC_UNINITIALIZED){
 		fprintf(stderr, "%s: stack register ", progname);
 		dc_show_id(stderr, stackid, " is empty\n");
 		return DC_FAIL;
@@ -411,6 +415,44 @@ dc_register_pop DC_DECLARG((stackid, result))
 }
 
 
+/* cyclically rotate the "n" topmost elements of the stack;
+ *   negative "n" rotates forward (topomost element becomes n-th deep)
+ *   positive "n" rotates backward (topmost element becomes 2nd deep)
+ *
+ * If stack depth is less than "n", whole stack is rotated
+ * (without raising an error).
+ */
+void
+dc_stack_rotate(int n)
+{
+	dc_list *p; /* becomes bottom of sub-stack */
+	dc_list *r; /* predecessor of "p" */
+	int absn = n<0 ? -n : n;
+
+	/* always do nothing for empty stack or degenerate rotation depth */
+	if (!dc_stack || absn < 2)
+		return;
+	/* find bottom of rotation sub-stack */
+	r = NULL;
+	for (p=dc_stack; p->link && --absn>0; p=p->link)
+		r = p;
+	/* if stack has only one element, treat rotation as no-op */
+	if (!r)
+		return;
+	/* do the rotation, in appropriate direction */
+	if (n > 0) {
+		r->link = p->link;
+		p->link = dc_stack;
+		dc_stack = p;
+	} else {
+		dc_list *new_tos = dc_stack->link;
+		dc_stack->link = p->link;
+		p->link = dc_stack;
+		dc_stack = new_tos;
+	}
+}
+
+
 /* tell how many entries are currently on the evaluation stack */
 int
 dc_tell_stackdepth DC_DECLVOID()
@@ -418,7 +460,7 @@ dc_tell_stackdepth DC_DECLVOID()
 	dc_list *n;
 	int depth=0;
 
-	for (n=dc_stack; n; n=n->link)
+	for (n=dc_stack; n!=NULL; n=n->link)
 		++depth;
 	return depth;
 }
@@ -442,7 +484,7 @@ dc_tell_length DC_DECLARG((value, discard_p))
 		if (discard_p == DC_TOSS)
 			dc_free_num(&value.v.number);
 	} else if (value.dc_type == DC_STRING) {
-		length = dc_strlen(value.v.string);
+		length = (int) dc_strlen(value.v.string);
 		if (discard_p == DC_TOSS)
 			dc_free_str(&value.v.string);
 	} else {
@@ -462,7 +504,7 @@ dc_printall DC_DECLARG((obase))
 {
 	dc_list *n;
 
-	for (n=dc_stack; n; n=n->link)
+	for (n=dc_stack; n!=NULL; n=n->link)
 		dc_print(n->value, obase, DC_WITHNL, DC_KEEP);
 }
 
@@ -475,7 +517,7 @@ dc_get_stacked_array DC_DECLARG((array_id))
 	int array_id DC_DECLEND
 {
 	dc_list *r = dc_register[regmap(array_id)];
-	return r ? r->array : NULL;
+	return r == NULL ? NULL : r->array;
 }
 
 /* set the current array head for the named array */
@@ -488,7 +530,16 @@ dc_set_stacked_array DC_DECLARG((array_id, new_head))
 
 	array_id = regmap(array_id);
 	r = dc_register[array_id];
-	if ( ! r )
+	if (r == NULL)
 		r = dc_register[array_id] = dc_alloc();
 	r->array = new_head;
 }
+
+
+/*
+ * Local Variables:
+ * mode: C
+ * tab-width: 4
+ * End:
+ * vi: set ts=4 :
+ */