[M3devel] the meaning of -FIRST(INTEGER)?

[Jay K]

So..I have m3back using Target.Int a bunch.

And converting back and forth some between Target.Int and

INTEGER and doing match with Target.Int.

And various operations can fail.

 

 

And my current diff results in:

 

 

  new source -> compiling Lex.m3  
  "..\src\fmtlex\Lex.m3", line 227: doneg: Negate overflowed  
  "..\src\fmtlex\Lex.m3", line 343: doneg: Negate overflowed  
  2 errors encountered  
  new source -> compiling Scan.i3  

 

 

  which is nice to see, it means my code is actually running.  

 

 

  So I look at the code in question:  

 

 

  PROCEDURE ReadNumber(rd: Rd.T; defaultBase: [2..16]; signed: BOOLEAN): Word.T  
  VAR c: CHAR; sign: [0..1]; res: Word.T; BEGIN 
...

    IF signed AND
       ((sign = 0 AND Word.GT(res, LAST(INTEGER))) OR
        (sign = 1 AND Word.GT(res, -FIRST(INTEGER)))) THEN
      RAISE FloatMode.Trap(FloatMode.Flag.IntOverflow)
....

 

 

-FIRST(INTEGER).

 

 

What is that supposed to do?

 

 

I mean, I kind of know, I'm slightly playing stupid, partly not.

Does the compiler know what is an INTEGER vs. what is a "Word"?

Or it is just obligated to assume everything is a Word?

 To do the negation at compile time and ignore the overflow?

 

 

Does the language need work here?

I mean, like, -FIRST(INTEGER), that is a problematic expression, isn't it?

 

 

 - Jay

 
 		 	   		  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://m3lists.elegosoft.com/pipermail/m3devel/attachments/20100120/70e3767e/attachment-0001.html>