From: ruvim.pinka@gmail.com   
      
   On 2024-05-24 15:56, Anton Ertl wrote:   
   > melahi_ahmed@yahoo.fr (Ahmed) writes:   
   >>   
   >>   In Forth it is a bit messier because you   
   >>   want a signature like   
   >>   
   >>   
   >>    : d/dx ( xt -- xt ) .... ;   
   >   
   > Most probably he meant ( xt1 -- xt2 )   
      
      
      
   Do you mean that ( xt -- xt ) is an incorrect stack diagram for this case?   
      
   I always thought that such use is correct. Because formally "xt"   
   (without an index) only denotes the data type, not a data value.   
      
   And "( xt -- xt )" does not mean that the data values before execution   
   and after execution are the same, since they may still be different.   
      
   In a stack diagram, the same data type symbols with the same indices   
   usually denote the same data value. Otherwise, if data values are not   
   mentioned (like "0", "-1", etc), it is unknown from the stack diagram   
   where the values are the same. Since different symbols in the does not   
   mean different data values. For example "abs ( n -- +n )" — in some   
   cases the data values "before" and "after" are the same.   
      
      
   --   
   Ruvim   
      
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