Add relative address and at functions

doc/teapot.lyx

@@ -5393,20 +5393,8 @@ l
 \emph default
 ) 
 \series default
-returns the value of the cell at position 
+returns the value of the cell at the specified location.
-\emph on
+ In the first form, if any of 
-x
-\emph default
-, 
-\emph on
-y
-\emph default
-, 
-\emph on
-z
-\emph default
-.
- If any of 
 \emph on
 x
 \emph default
@@ -5466,8 +5454,29 @@ y
 z
 \emph default
 ]]])
+\begin_inset space ~
+\end_inset
+
+|
+\begin_inset space ~
+\end_inset
+
+
 \series default
-returns a pointer to the cell at location 
+&
+\series medium
+(location
+\emph on
+
+\begin_inset space ~
+\end_inset
+
+l
+\emph default
+) 
+\series default
+returns the specified location.
+ In the first form, if any of 
 \emph on
 x
 \emph default
@@ -5475,30 +5484,65 @@ x
 \emph on
 y
 \emph default
-, 
+ or 
 \emph on
 z
 \emph default
-.
+ is omitted, the coordinate of the cell is used.
- If 
+ The second form is in fact a no-op, but it is allowed for convenience
-\emph on
+\end_layout
-z
-\emph default
- is omitted, the 
-\emph on
-z
-\emph default
- position of the current cell is used.
- If 
-\emph on
-y
-\emph default
- is missing as well, the 
-\emph on
-y
-\emph default
- position (row) of the cell is used.
 
+\begin_layout Description
+R() Exactly the same as 
+\series bold
+@
+\series default
+, except the coordinates of the argument are interpreted as an offset to
+ the current location (rather than as absolute coordinates in the sheet);
+ think 
+\begin_inset Quotes eld
+\end_inset
+
+R
+\begin_inset Quotes erd
+\end_inset
+
+ for 
+\begin_inset Quotes eld
+\end_inset
+
+relative.
+\begin_inset Quotes erd
+\end_inset
+
+ Thus R(-1) returns the value of the cell immediately to the left of this
+ one.
+\end_layout
+
+\begin_layout Description
+D() Exactly the same as 
+\series bold
+&
+\series default
+, except the coordinates of the argument are added to the current location.
+ Think 
+\begin_inset Quotes eld
+\end_inset
+
+D
+\begin_inset Quotes erd
+\end_inset
+
+ for 
+\begin_inset Quotes eld
+\end_inset
+
+displaced (by).
+\begin_inset Quotes erd
+\end_inset
+
+ Thus, D(-1) returns the location of the cell immediately to the left of
+ this one.
 \end_layout
 
 \begin_layout Description

src/common/func.c

@@ -305,68 +305,15 @@ static double deg2rad(double x)
 
 #define INTPATIBLE(t) (t.type == INT || t.type == EMPTY)
 
-/* @ */ /*{{{*/
+typedef enum {ABSOLUTE, RELATIVE} LocConvention;
-static Token at_func(int argc, const Token argv[])
-{
-  /* variables */ /*{{{*/
-  Token result;
-  Location tmp;
-  Dimensions dim;
-  /*}}}*/
-
-  /* asserts */ /*{{{*/
-  assert(argv!=(Token*)0);
-  /*}}}*/
-  if (argc==0)
-  /* return value at current location */ /*{{{*/
-  return (getvalue(upd_sheet, upd_l));
-  /*}}}*/
-  if (argc==1 && argv[0].type==LOCATION)
-  /* return value at location pointed to by argument */ /*{{{*/
-  return (getvalue(upd_sheet, argv[0].u.location));
-  /*}}}*/
-  LOCATION_GETS(tmp, upd_l);
-  if (argc==1 && (argv[0].type==INT || argv[0].type==EMPTY))
-  /* return value at x on current y,z */ /*{{{*/
-  {
-    if (argv[0].type == INT) tmp[X] = argv[0].u.integer;
-    return getvalue(upd_sheet, tmp);
-  }
-  /*}}}*/
-  if (argc==2 && INTPATIBLE(argv[0]) && INTPATIBLE(argv[1]))
-  /* return value at x,y on current z */ /*{{{*/
-  {
-    if (argv[0].type == INT) tmp[X] = argv[0].u.integer;
-    if (argv[1].type == INT) tmp[Y] = argv[1].u.integer;
-    return getvalue(upd_sheet, tmp);
-  }
-  /*}}}*/
-  if (argc==3 && INTPATIBLE(argv[0]) && INTPATIBLE(argv[1]) &&
-      INTPATIBLE(argv[2]))
-  /* return value at x,y,z */ /*{{{*/
-  {
-    for (dim = X; dim < HYPER; ++dim)
-      if (argv[dim].type == INT) tmp[dim] = argv[dim].u.integer;
-    return getvalue(upd_sheet, tmp);
-  }
-  /*}}}*/
-  else
-  /* return error */ /*{{{*/
-  {
-    result.type=EEK;
-    result.u.err=strcpy(malloc(strlen(_("Usage: @([integer x][,[integer y][,[integer z]]]) or @(location)"))+1),_("Usage: @([integer x][,[integer y][,[integer z]]]) or @(location)"));
-    return result;
-  }
-  /*}}}*/
-}
-/*}}}*/
 
 /* & */ /*{{{*/
-static Token adr_func(int argc, const Token argv[])
+static Token adr_func(int argc, const Token argv[], LocConvention lcon)
 {
   /* variables */ /*{{{*/
   Token result;
   Dimensions dim;
+  size_t i;
   /*}}}*/
 
   /* asserts */ /*{{{*/
@@ -374,47 +321,64 @@ static Token adr_func(int argc, const Token argv[])
   /*}}}*/
 
   LOCATION_GETS(result.u.location, upd_l);
-  if (argc==3 && INTPATIBLE(argv[0]) && INTPATIBLE(argv[1]) &&
+  if (argc == 1 && argv[0].type == LOCATION) return argv[0];
-      INTPATIBLE(argv[2]))
+  for (i = 0; i < argc && i < HYPER; ++i)
-  /* result is location of the given position */ /*{{{*/
   {
-    result.type=LOCATION;
+    if (!INTPATIBLE(argv[i])) break;
-    for (dim = X; dim < HYPER; ++dim)
+    if (lcon == ABSOLUTE) result.u.location[i] = argv[i].u.integer;
-      if (argv[dim].type == INT) result.u.location[dim] = argv[dim].u.integer;
+    else result.u.location[i] += argv[i].u.integer;
   }
-  /*}}}*/
+  if (i < argc)
-  else if (argc==2 && INTPATIBLE(argv[0]) && INTPATIBLE(argv[1]))
-  /* result is location of the given position in the current z layer */ /*{{{*/
-  {
-    result.type=LOCATION;
-    for (dim = X; dim <= Y; ++dim)
-      if (argv[dim].type == INT) result.u.location[dim] = argv[dim].u.integer;
-  }
-  /*}}}*/
-  else if (argc==1 && INTPATIBLE(argv[0]))
-  /* result is location of the given position in the current y,z layer */ /*{{{*/
-  {
-    result.type=LOCATION;
-    if (argv[0].type == INT) result.u.location[X] = argv[0].u.integer;
-  }
-  /*}}}*/
-  else if (argc==0)
-  /* result is location of the current position */ /*{{{*/
-  {
-    result.type=LOCATION;
-  }
-  /*}}}*/
-  else
-  /* result is type error */ /*{{{*/
   {
     result.type=EEK;
     result.u.err=strcpy(malloc(strlen(_("Usage: &([integer x][,[integer y][,[integer z]]])"))+1),_("Usage: &([integer x][,[integer y][,[integer z]]])"));
   }
-  /*}}}*/
+  else 
+    result.type = LOCATION;
   return result;
 }
 /*}}}*/
 
+/* @ */ /*{{{*/
+static Token at_func(int argc, const Token argv[], LocConvention lcon)
+{
+  Token location;
+
+  location = adr_func(argc, argv, lcon);
+  if (location.type == EEK)
+  {
+    Token result;
+    result.type = EEK;
+    char *pref = _("Inside @: ");
+    result.u.err = malloc(strlen(location.u.err) + strlen(pref) + 1);
+    strcpy(result.u.err, pref);
+    strcat(result.u.err, location.u.err);
+    tfree(&location);
+    return result;
+  }
+  return getvalue(upd_sheet, location.u.location);
+}
+
+static Token abs_adr_func(int argc, const Token argv[])
+{
+  return adr_func(argc, argv, ABSOLUTE);
+}
+
+static Token abs_at_func(int argc, const Token argv[])
+{
+  return at_func(argc, argv, ABSOLUTE);
+}
+
+static Token rel_adr_func(int argc, const Token argv[])
+{
+  return adr_func(argc, argv, RELATIVE);
+}
+
+static Token rel_at_func(int argc, const Token argv[])
+{
+  return at_func(argc, argv, RELATIVE);
+}
+
 /* x */ /*{{{*/
 static Token x_func(int argc, const Token argv[])
 {
@@ -1446,8 +1410,8 @@ static Token time_func(int argc, const Token argv[])
    compatible, new entries should be appended. */
 Tfunc tfunc[]=
 {
-  { "@", at_func },
+  { "@", abs_at_func },
-  { "&", adr_func },
+  { "&", abs_adr_func },
   { "x", x_func },
   { "y", y_func },
   { "z", z_func },
@@ -1489,6 +1453,8 @@ Tfunc tfunc[]=
   { "time", time_func },
   { "bitand", bitand_func },
   { "bitor", bitor_func },
+  { "D", rel_adr_func },
+  { "R", rel_at_func },
   { "", (Token (*)(int, const Token[]))0 }
 };
 /*}}}*/