Add "pager" variable and "unset" command.

* src/gdbmtool.c (command_tab) <unset>: New command.
(run_command): Get pager value from the variable.
* src/gdbmtool.h (VAR_ERR_NOTSET): New error code.
(variable_is_true): New function. Replaces variable_is_set,
which changed semantics.
* src/gram.y: Implement the unset command.
* src/var.c: Support the "unset variable" notion.
(VARF_INIT): New flag.
(VAR_IS_SET): New define.
(vartab): Mark initialized variables with VARF_INIT.
New variable "pager".
(open_hook): v can be NULL.
(variable_set): NULL value unsets the variable.
(variable_unset): New function.
(variable_get): Return VAR_ERR_NOTSET if the variable is
not set.
(variable_is_true): Renamed from variable_is_set.
(variable_is_set): New function.

* src/gdbmdefs.h: Fix some typos.

1 files changed, 32 insertions, 4 deletions

diff --git a/src/gram.y b/src/gram.y
index a54ef0e..b939d8e 100644
--- a/src/gram.y
+++ b/src/gram.y
@@ -31,7 +31,9 @@ struct dsegm *dsdef[DS_MAX];
        T_PAD "pad"
        T_DEF "define"
        T_SET "set"
+       T_UNSET "unset"
        T_BOGUS
+
 %token <cmd> T_CMD "command verb"
 %token <num> T_NUM "number"
 %token <string> T_IDENT "identifier" T_WORD "word"
@@ -244,14 +246,15 @@ set       : T_SET
             {
 	      variable_print_all (stdout);
             }
-          | T_SET varlist
+          | T_SET asgnlist
+	  | T_UNSET varlist
           ;
 
-varlist   : var
-          | varlist var
+asgnlist  : asgn
+          | asgnlist asgn
           ;
 
-var       : T_IDENT
+asgn      : T_IDENT
             {
 	      int t = 1;
 	      int rc;
@@ -304,6 +307,31 @@ var       : T_IDENT
 	      free ($3);
 	    }
           ;
+
+varlist   : var
+          | varlist var
+          ;
+
+var       : T_IDENT
+            {
+	      int rc = variable_unset ($1);
+	      switch (rc)
+		{
+		case VAR_OK:
+		  break;
+		  
+		case VAR_ERR_NOTDEF:
+		  lerror (&@1, _("no such variable: %s"), $1);
+		  break;
+
+		case VAR_ERR_BADVALUE:
+		  lerror (&@1, _("%s: variable cannot be unset"), $1);
+		  break;
+		}
+	      free($1);
+	    }
+          ;
+
 %%
 
 void