[Pspp-cvs] Changes to pspp/src/do-if.c

[Ben Pfaff]

Index: pspp/src/do-if.c
diff -u pspp/src/do-if.c:1.12 pspp/src/do-if.c:1.13
--- pspp/src/do-if.c:1.12       Sun Jul 31 21:42:46 2005
+++ pspp/src/do-if.c    Thu Nov  3 06:21:46 2005
@@ -18,7 +18,7 @@
    02110-1301, USA. */
 
 #include <config.h>
-#include "do-ifP.h"
+#include "ctl-stack.h"
 #include "error.h"
 #include <stdlib.h>
 #include "alloc.h"
@@ -32,159 +32,95 @@
 #include "gettext.h"
 #define _(msgid) gettext (msgid)
 
-#include "debug-print.h"
-
-/* *INDENT-OFF* */
-/* Description of DO IF transformations:
-
-   DO IF has two transformations.  One is a conditional jump around
-   a false condition.  The second is an unconditional jump around
-   the rest of the code after a true condition.  Both of these types
-   have their destinations backpatched in by the next clause (ELSE IF,
-   END IF).
-
-   The characters `^V<>' are meant to represent arrows.
-
-   1. DO IF
- V<<<<if false
- V
- V *. Transformations executed when the condition on DO IF is true.
- V
- V 2. GOTO>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>V
- V                                                                    V
- >>1. ELSE IF                                                         V
- V<<<<if false                                                        V
- V                                                                    V
- V *. Transformations executed when condition on 1st ELSE IF is true.  V
- V                                                                    V
- V 2. GOTO>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>V
- V                                                                    V
- >>1. ELSE IF                                                         V
- V<<<<if false                                                        V
- V                                                                    V
- V *. Transformations executed when condition on 2nd ELSE IF is true.  V
- V                                                                    V
- V 2. GOTO>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>V
- V                                                                    V
- >>*. Transformations executed when no condition is true. (ELSE)       V
-                                                                      V
-   *. Transformations after DO IF structure.<<<<<<<<<<<<<<<<<<<<<<<<<<<<
+/* DO IF, ELSE IF, and ELSE are translated as a single
+   transformation that evaluates each condition and jumps to the
+   start of the appropriate block of transformations.  Each block
+   of transformations (except for the last) ends with a
+   transformation that jumps past the remaining blocks.
+
+   So, the following code:
+
+       DO IF a.             
+       ...block 1...
+       ELSE IF b.
+       ...block 2...
+       ELSE.
+       ...block 3...
+       END IF.
+
+   is effectively translated like this:
+
+       IF a GOTO 1, IF b GOTO 2, ELSE GOTO 3.
+       1: ...block 1...
+          GOTO 4
+       2: ...block 2...
+          GOTO 4
+       3: ...block 3...
+       4:
 
 */
-/* *INDENT-ON* */
 
-static struct do_if_trns *parse_do_if (void);
-static void add_ELSE_IF (struct do_if_trns *);
-static trns_proc_func goto_trns_proc, do_if_trns_proc;
+/* A conditional clause. */
+struct clause 
+  {
+    struct expression *condition; /* Test expression; NULL for ELSE clause. */
+    int target_index;           /* Transformation to jump to if true. */
+  };
+
+/* DO IF transformation. */
+struct do_if_trns
+  {
+    struct clause *clauses;     /* Clauses. */
+    size_t clause_cnt;          /* Number of clauses. */
+    int past_END_IF_index;      /* Transformation just past last clause. */
+  };
+
+static struct ctl_class do_if_class;
+
+static int parse_clause (struct do_if_trns *);
+static void add_clause (struct do_if_trns *,
+                        struct expression *condition, int target_index);
+static void add_else (struct do_if_trns *);
+
+static bool has_else (struct do_if_trns *);
+static bool must_not_have_else (struct do_if_trns *);
+static void close_do_if (void *do_if);
+
+static trns_proc_func do_if_trns_proc, break_trns_proc;
 static trns_free_func do_if_trns_free;
 
 /* Parse DO IF. */
 int
 cmd_do_if (void)
 {
-  struct do_if_trns *t;
-
-  /* Parse the transformation. */
-  t = parse_do_if ();
-  if (!t)
-    return CMD_FAILURE;
+  struct do_if_trns *do_if = xmalloc (sizeof *do_if);
+  do_if->clauses = NULL;
+  do_if->clause_cnt = 0;
 
-  /* Finish up the transformation, add to control stack, add to
-     transformation list. */
-  t->brk = NULL;
-  t->ctl.type = CST_DO_IF;
-  t->ctl.down = ctl_stack;
-  t->ctl.trns = (struct trns_header *) t;
-  t->ctl.brk = NULL;
-  t->has_else = 0;
-  ctl_stack = &t->ctl;
-  add_transformation ((struct trns_header *) t);
+  ctl_stack_push (&do_if_class, do_if);
+  add_transformation (do_if_trns_proc, do_if_trns_free, do_if);
 
-  return CMD_SUCCESS;
+  return parse_clause (do_if);
 }
 
 /* Parse ELSE IF. */
 int
 cmd_else_if (void)
 {
-  /* Transformation created. */
-  struct do_if_trns *t;
-
-  /* Check that we're in a pleasing situation. */
-  if (!ctl_stack || ctl_stack->type != CST_DO_IF)
-    {
-      msg (SE, _("There is no DO IF to match with this ELSE IF."));
-      return CMD_FAILURE;
-    }
-  if (((struct do_if_trns *) ctl_stack->trns)->has_else)
-    {
-      msg (SE, _("The ELSE command must follow all ELSE IF commands "
-                "in a DO IF structure."));
-      return CMD_FAILURE;
-    }
-
-  /* Parse the transformation. */
-  t = parse_do_if ();
-  if (!t)
+  struct do_if_trns *do_if = ctl_stack_top (&do_if_class);
+  if (do_if == NULL || !must_not_have_else (do_if))
     return CMD_FAILURE;
-
-  /* Stick in the breakout transformation. */
-  t->brk = xmalloc (sizeof *t->brk);
-  t->brk->h.proc = goto_trns_proc;
-  t->brk->h.free = NULL;
-
-  /* Add to list of transformations, add to string of ELSE IFs. */
-  add_transformation ((struct trns_header *) t->brk);
-  add_transformation ((struct trns_header *) t);
-
-  add_ELSE_IF (t);
-
-  if (token != '.')
-    {
-      msg (SE, _("End of command expected."));
-      return CMD_TRAILING_GARBAGE;
-    }
-
-  return CMD_SUCCESS;
+  return parse_clause (do_if);
 }
 
 /* Parse ELSE. */
 int
 cmd_else (void)
 {
-  struct do_if_trns *t;
-
-  /* Check that we're in a pleasing situation. */
-  if (!ctl_stack || ctl_stack->type != CST_DO_IF)
-    {
-      msg (SE, _("There is no DO IF to match with this ELSE."));
-      return CMD_FAILURE;
-    }
-  
-  if (((struct do_if_trns *) ctl_stack->trns)->has_else)
-    {
-      msg (SE, _("There may be at most one ELSE clause in each DO IF "
-                "structure.  It must be the last clause."));
-      return CMD_FAILURE;
-    }
-
-  /* Note that the ELSE transformation is *not* added to the list of
-     transformations.  That's because it doesn't need to do anything.
-     Its goto transformation *is* added, because that's necessary.
-     The main DO IF do_if_trns is the destructor for this ELSE
-     do_if_trns. */
-  t = xmalloc (sizeof *t);
-  t->next = NULL;
-  t->brk = xmalloc (sizeof *t->brk);
-  t->brk->h.proc = goto_trns_proc;
-  t->brk->h.free = NULL;
-  t->cond = NULL;
-  add_transformation ((struct trns_header *) t->brk);
-  t->h.index = t->brk->h.index + 1;
-
-  /* Add to string of ELSE IFs. */
-  add_ELSE_IF (t);
-
+  struct do_if_trns *do_if = ctl_stack_top (&do_if_class);
+  if (do_if == NULL || !must_not_have_else (do_if))
+    return CMD_FAILURE;
+  add_else (do_if);
   return lex_end_of_command ();
 }
 
@@ -192,133 +128,147 @@
 int
 cmd_end_if (void)
 {
-  /* List iterator. */
-  struct do_if_trns *iter;
-
-  /* Check that we're in a pleasing situation. */
-  if (!ctl_stack || ctl_stack->type != CST_DO_IF)
-    {
-      msg (SE, _("There is no DO IF to match with this END IF."));
-      return CMD_FAILURE;
-    }
-
-  /* Chain down the list, backpatching destinations for gotos. */
-  iter = (struct do_if_trns *) ctl_stack->trns;
-  for (;;)
-    {
-      if (iter->brk)
-       iter->brk->dest = n_trns;
-      iter->missing_jump = n_trns;
-      if (iter->next)
-       iter = iter->next;
-      else
-       break;
-    }
-  iter->false_jump = n_trns;
+  struct do_if_trns *do_if = ctl_stack_top (&do_if_class);
+  if (do_if == NULL)
+    return CMD_FAILURE;
 
-  /* Pop control stack. */
-  ctl_stack = ctl_stack->down;
+  ctl_stack_pop (do_if);
 
   return lex_end_of_command ();
 }
 
-/* Adds an ELSE IF or ELSE to the chain of them that hangs off the
-   main DO IF. */
+/* Closes out DO_IF, by adding a sentinel ELSE clause if
+   necessary and setting past_END_IF_index. */
 static void
-add_ELSE_IF (struct do_if_trns * t)
+close_do_if (void *do_if_) 
 {
-  /* List iterator. */
-  struct do_if_trns *iter;
-
-  iter = (struct do_if_trns *) ctl_stack->trns;
-  while (iter->next)
-    iter = iter->next;
-  assert (iter != NULL);
-
-  iter->next = t;
-  iter->false_jump = t->h.index;
+  struct do_if_trns *do_if = do_if_;
+  
+  if (!has_else (do_if)) 
+    add_else (do_if);
+  do_if->past_END_IF_index = next_transformation ();
 }
 
-/* Parses a DO IF or ELSE IF command and returns a pointer to a mostly
-   filled in transformation. */
-static struct do_if_trns *
-parse_do_if (void)
+/* Adds an ELSE clause to DO_IF pointing to the next
+   transformation. */
+static void
+add_else (struct do_if_trns *do_if) 
 {
-  struct do_if_trns *t;
-  struct expression *e;
+  assert (!has_else (do_if));
+  add_clause (do_if, NULL, next_transformation ());
+}
 
-  e = expr_parse (default_dict, EXPR_BOOLEAN);
-  if (!e)
-    return NULL;
-  if (token != '.')
+/* Returns true if DO_IF does not yet have an ELSE clause.
+   Reports an error and returns false if it does already. */
+static bool
+must_not_have_else (struct do_if_trns *do_if) 
+{
+  if (has_else (do_if))
     {
-      expr_free (e);
-      lex_error (_("expecting end of command"));
-      return NULL;
+      msg (SE, _("This command may not follow ELSE in DO IF...END IF."));
+      return false;
     }
+  else
+    return true;
+}
 
-  t = xmalloc (sizeof *t);
-  t->h.proc = do_if_trns_proc;
-  t->h.free = do_if_trns_free;
-  t->next = NULL;
-  t->cond = e;
+/* Returns true if DO_IF already has an ELSE clause,
+   false otherwise. */
+static bool
+has_else (struct do_if_trns *do_if) 
+{
+  return (do_if->clause_cnt != 0
+          && do_if->clauses[do_if->clause_cnt - 1].condition == NULL);
+}
+
+/* Parses a DO IF or ELSE IF expression and appends the
+   corresponding clause to DO_IF.  Checks for end of command and
+   returns a command return code. */
+static int
+parse_clause (struct do_if_trns *do_if)
+{
+  struct expression *condition;
+
+  condition = expr_parse (default_dict, EXPR_BOOLEAN);
+  if (condition == NULL)
+    return CMD_FAILURE;
+
+  add_clause (do_if, condition, next_transformation ());
 
-  return t;
+  return lex_end_of_command ();
 }
 
-/* Executes a goto transformation. */
-static int 
-goto_trns_proc (struct trns_header * t, struct ccase * c UNUSED,
-                int case_num UNUSED)
+/* Adds a clause to DO_IF that tests for the given CONDITION and,
+   if true, jumps to TARGET_INDEX. */
+static void
+add_clause (struct do_if_trns *do_if,
+            struct expression *condition, int target_index) 
 {
-  return ((struct goto_trns *) t)->dest;
+  struct clause *clause;
+
+  if (do_if->clause_cnt > 0)
+    add_transformation (break_trns_proc, NULL, do_if);
+
+  do_if->clauses = xnrealloc (do_if->clauses,
+                              do_if->clause_cnt + 1, sizeof *do_if->clauses);
+  clause = &do_if->clauses[do_if->clause_cnt++];
+  clause->condition = condition;
+  clause->target_index = target_index;
 }
 
+/* DO IF transformation procedure.
+   Checks each clause and jumps to the appropriate
+   transformation. */
 static int 
-do_if_trns_proc (struct trns_header * trns, struct ccase * c,
-                 int case_num UNUSED)
+do_if_trns_proc (void *do_if_, struct ccase *c, int case_num UNUSED)
 {
-  struct do_if_trns *t = (struct do_if_trns *) trns;
-  double boolean;
+  struct do_if_trns *do_if = do_if_;
+  struct clause *clause;
 
-  boolean = expr_evaluate_num (t->cond, c, case_num);
-  if (boolean == 1.0)
-    {
-      debug_printf ((_("DO IF %d: true\n"), t->h.index));
-      return -1;
-    }
-  else if (boolean == 0.0)
-    {
-      debug_printf ((_("DO IF %d: false\n"), t->h.index));
-      return t->false_jump;
-    }
-  else
+  for (clause = do_if->clauses; clause < do_if->clauses + do_if->clause_cnt;
+       clause++) 
     {
-      debug_printf ((_("DO IF %d: missing\n"), t->h.index));
-      return t->missing_jump;
+      if (clause->condition != NULL)
+        {
+          double boolean = expr_evaluate_num (clause->condition, c, case_num);
+          if (boolean == 1.0)
+            return clause->target_index;
+          else if (boolean == SYSMIS)
+            return do_if->past_END_IF_index;
+        }
+      else 
+        return clause->target_index;
     }
+  return do_if->past_END_IF_index;
 }
 
+/* Frees a DO IF transformation. */
 static void 
-do_if_trns_free (struct trns_header * trns)
+do_if_trns_free (void *do_if_)
 {
-  struct do_if_trns *t = (struct do_if_trns *) trns;
-  expr_free (t->cond);
+  struct do_if_trns *do_if = do_if_;
+  struct clause *clause;
 
-  /* If brk is NULL then this is the main DO IF; therefore we
-     need to chain down to the ELSE and delete it. */
-  if (t->brk == NULL)
-    {
-      struct do_if_trns *iter = t->next;
-      while (iter)
-       {
-         if (!iter->cond)
-           {
-             /* This is the ELSE. */
-             free (iter);
-             break;
-           }
-         iter = iter->next;
-       }
-    }
+  for (clause = do_if->clauses; clause < do_if->clauses + do_if->clause_cnt;
+       clause++)
+    expr_free (clause->condition);
+  free (do_if->clauses);
+  free (do_if);
+}
+
+/* Breaks out of a DO IF construct. */
+static int 
+break_trns_proc (void *do_if_, struct ccase *c UNUSED, int case_num UNUSED)
+{
+  struct do_if_trns *do_if = do_if_;
+
+  return do_if->past_END_IF_index;
 }
+
+/* DO IF control structure class definition. */
+static struct ctl_class do_if_class = 
+  {
+    "DO IF",
+    "END IF",
+    close_do_if,
+  };