diff --git a/parser.y b/parser.y
index 759efd3..1125e76 100644
--- a/parser.y
+++ b/parser.y
@@ -8,8 +8,8 @@
   int integer;
   double fp;
   char *string;
-  struct { double width; double height; } size;
-  struct { int first; int last; } range;
+  page_size_t size;
+  range_t range;
 }
 
 %token <integer> INTEGER
diff --git a/scanner.l b/scanner.l
index 81abb0c..1227f6e 100644
--- a/scanner.l
+++ b/scanner.l
@@ -1,5 +1,5 @@
 /*
-$Id: scanner.l,v 1.9 2001/12/30 08:29:50 eric Exp $
+$Id: scanner.l,v 1.10 2001/12/30 09:09:08 eric Exp $
 */
 
 %option case-insensitive
@@ -8,9 +8,9 @@ $Id: scanner.l,v 1.9 2001/12/30 08:29:50 eric Exp $
 %{
 #include <stdio.h>
 #include <string.h>
-#include "parser.tab.h"
 #include "type.h"
 #include "semantics.h"
+#include "parser.tab.h"
 
 #ifdef SCANNER_DEBUG
 #define LDBG(x) printf x
diff --git a/semantics.c b/semantics.c
index 5186a66..08adb36 100644
--- a/semantics.c
+++ b/semantics.c
@@ -1,24 +1,55 @@
+#include <stdlib.h>
+#include <string.h>
 #include <stdio.h>
 
 #include "type.h"
-#include "parser.tab.h"
 #include "semantics.h"
+#include "parser.tab.h"
 
 
 FILE *yyin;
 int line;  /* line number in spec file */
 
 
-int input_count;   /* total input pages in spec */
-int output_count;  /* total output pages in spec */
+int input_page_count;   /* total input pages in spec */
+int output_page_count;  /* total output pages in spec */
+
+
+input_context_t *current_input_context;
 
 
 void input_push_context (input_context_type_t type)
 {
+  input_context_t *new_input_context;
+
+  new_input_context = malloc (sizeof (input_context_t));
+  if (! new_input_context)
+    {
+      fprintf (stderr, "failed to calloc an input context\n");
+      return;
+    }
+
+  if (current_input_context)
+    {
+      memcpy (new_input_context, current_input_context, sizeof (input_context_t));
+      new_input_context->page_count = 0;
+    }
+  else
+    memset (new_input_context, 0, sizeof (input_context_t));
+
+  new_input_context->parent_input_context = current_input_context;
+  current_input_context = new_input_context;
 };
 
 void input_pop_context (void)
 {
+  if (! current_input_context)
+    {
+      fprintf (stderr, "failed to pop an input context\n");
+      return;
+    }
+
+  current_input_context = current_input_context->parent_input_context;
 };
 
 void input_set_file (char *name)
@@ -27,20 +58,25 @@ void input_set_file (char *name)
 
 void input_images (int first, int last)
 {
-  input_count += ((last - first) + 1);
+  input_page_count += ((last - first) + 1);
   if (first == last)
     printf ("image %d\n", first);
   else
-    printf ("iamges %d..%d\n", first, last);
+    printf ("images %d..%d\n", first, last);
 }
 
+
+void output_push_context (void)
+{
+};
+
 void output_set_file (char *name)
 {
 };
 
 void output_pages (int first, int last)
 {
-  output_count += ((last - first) + 1);
+  output_page_count += ((last - first) + 1);
   if (first == last)
     printf ("page %d\n", first);
   else
@@ -67,8 +103,20 @@ boolean parse_spec_file (char *fn)
 
   line = 1;
 
+  input_push_context (INPUT_CONTEXT_ALL);  /* create initial input context */
+  output_push_context ();  /* create initial output context */
+
   yyparse ();
 
+  if (input_page_count != output_page_count)
+    {
+      fprintf (stderr, "input page count %d != output page count %d\n",
+	       input_page_count, output_page_count);
+      goto fail;
+    }
+
+  fprintf (stderr, "%d pages specified\n", input_page_count);
+
   result = 1;
 
  fail:
diff --git a/semantics.h b/semantics.h
index ffb40d4..f7e583f 100644
--- a/semantics.h
+++ b/semantics.h
@@ -1,3 +1,23 @@
+typedef struct 
+{
+  double width;
+  double height;
+} page_size_t;
+
+typedef struct
+{
+  int first; 
+  int last;
+ } range_t;
+
+typedef struct
+{
+  double left;
+  double right;
+  double top;
+  double bottom;
+} crop_t;
+
 typedef enum
 {
   INPUT_CONTEXT_ALL,
@@ -6,11 +26,44 @@ typedef enum
 } input_context_type_t;
 
 
+typedef struct
+{
+  boolean has_size;
+  page_size_t size;
+
+  boolean has_rotation;
+  int rotation;
+
+  boolean has_crop;
+  crop_t crop;
+} input_modifiers_t;
+
+
+typedef enum
+{
+  INPUT_MODIFIER_ALL,
+  INPUT_MODIFIER_ODD,
+  INPUT_MODIFIER_EVEN,
+  INPUT_MODIFIER_TYPE_COUNT  /* must be last */
+} input_modifier_type_t;
+
+
+typedef struct input_context_t
+{
+  struct input_context_t *parent_input_context;
+
+  int page_count;  /* how many pages reference this context,
+		      including those from subcontexts */
+
+  input_modifiers_t modifiers [INPUT_MODIFIER_TYPE_COUNT];
+} input_context_t;
+
+
 extern int line;  /* line number in spec file */
 
 
-extern int input_count;   /* total input pages in spec */
-extern int output_count;  /* total output pages in spec */
+extern int input_page_count;   /* total input pages in spec */
+extern int output_page_count;  /* total output pages in spec */
 
 
 boolean parse_spec_file (char *fn);
diff --git a/t2p.c b/t2p.c
index 6d61b11..8b91c2d 100644
--- a/t2p.c
+++ b/t2p.c
@@ -1,7 +1,7 @@
 /*
  * tiffg4: reencode a bilevel TIFF file as a single-strip TIFF Class F Group 4
  * Main program
- * $Id: t2p.c,v 1.4 2001/12/30 08:29:50 eric Exp $
+ * $Id: t2p.c,v 1.5 2001/12/30 09:09:08 eric Exp $
  * Copyright 2001 Eric Smith <eric@brouhaha.com>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -28,8 +28,8 @@
 
 #include "type.h"
 #include "bitblt.h"
-#include "parser.tab.h"
 #include "semantics.h"
+#include "parser.tab.h"
 #include "tiff2pdf.h"
 
 
diff --git a/tumble.c b/tumble.c
index 0cd9b33..d0c7332 100644
--- a/tumble.c
+++ b/tumble.c
@@ -1,7 +1,7 @@
 /*
  * tiffg4: reencode a bilevel TIFF file as a single-strip TIFF Class F Group 4
  * Main program
- * $Id: tumble.c,v 1.4 2001/12/30 08:29:50 eric Exp $
+ * $Id: tumble.c,v 1.5 2001/12/30 09:09:08 eric Exp $
  * Copyright 2001 Eric Smith <eric@brouhaha.com>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -28,8 +28,8 @@
 
 #include "type.h"
 #include "bitblt.h"
-#include "parser.tab.h"
 #include "semantics.h"
+#include "parser.tab.h"
 #include "tiff2pdf.h"