[Jgeneral] Two requests for j enhancement.

[David Ward Lambert]

Requests for j enhancement based on j64-602, discovered while
investigating project Euler problem 277.

0) Define inverses for linear polynomial evaluation.

      0 p.^:_1(0)
   |domain error
   |   0     p.^:_1(0)
      0 1 p.^:_1(8)
   |domain error
   |   0 1     p.^:_1(8)



1) Improve error messages.

   Domain error does not  isolate "@".  The interpreter COULD identify
   the problem.

      %&3...@_1 2&p.
   |domain error
   |       %&3...@_1 2&p.

   jforc/parsing_and_execution_ii.htm#_Toc191734586

        unprocessedWords stackTopFour restOfStack

        $vcncncv  
        $vcncnc v 
        $vcncn cv 
        $vcnc ncv 
        $vcn cncv 
        $vc ncnc v
        $v cncn cv
        $ vcnc ncv
         $vcn cncv conj rule 4, replace for "vcn" "v"  $v cncv
         $vcn cv   conj rule 4, replace for "vcn" "v"  $v cv
         $vcv      conj rule 4, replace for "vcv" "v"  $v
         $v

   Result is a verb.  Consider the data types.

         $vcn cncv conj rule 4, replace for "vcn" "v"  $v cncv
            %&3   verb & noun  works
         $vcn cv   conj rule 4, replace for "vcn" "v"  $v cv
            anonymousVerb @ noun
            Domain error, v...@n is illegal.
            Arguments to atop cause the problem.

Thanks,
Dave.


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