CAS command question

[compsystems]

Sorry my native language is not english

The RIGHT & LEFT functions can be programmed with the PART command, but you have to enter the expressions in quotation marks, so that the expression is taken as written

PHP Code:

testpartcas( ):=
  begin
    local expr1:='(x+y9)<4';  
    return([ part(expr1,1), part(expr1,2) ]);
  end;
  /// testpartcas() -> [ x+y, 4 ] // ok
#end 


Related to the manipulation of expressions. The programs that I want to made are step by step, if the expressions are rewritten, the logic of the algorithm is lost, with QUOTES, I solve this, but I have to ask the user, that input the expression in quotation marks, (Unnatural notation).

I repeat a previous question
My question for Parisse: how is it done within a program to convert the input inside a quotation mark?

I try the following, but it does not work

PHP Code:

#cas
  helpquote( id0 ):=
  begin
    local id1;
    id1 := quote(id0); // -> 'id0' =(
    print; print(id1);

    print( [ left(id1), right(id1) ] ); wait;

    return ( [ left(id1), right(id1) ] );
  end;
  // helpquote( (x+y)^(1+1)-3 ) -> [(x+y)^(1+1),-3] //  This would be the expected output.
  // helpquote( 4/2 ) -> [4 2] // This would be the expected output.
#end 


so we would need a new CAS command called RECALL

PHP Code:

id1 := quote( RECALL (id0) ); 


Another solution would be to interpret as a QUOTE EXPRESSION, if the arguments are within quotes,

PHP Code:

helpquote( 'id0' ):=
  begin ...