Re: ADA Popularity Discussion Request

From: Georg Bauhaus (sb463ba_at_l1-hrz.uni-duisburg.de)
Date: 09/09/04 

Date: Thu, 9 Sep 2004 01:47:46 +0000 (UTC)

jayessay <nospam@foo.com> wrote:

: Yes, and they don't happen at runtime if pre and post are checked
: during incremental development. If you don't do this, then you will
: likely have problems - just like if you don't get the types right in
: static languages.

Is it really much more time efficient, if pre and post checking is done
by an incrementing human? If so, how much?

 
: Your explanation above does not cover the logic error. I don't see
: right off how modular types catch that.

See below, there isn't a logic error, only a typo.

: with Text_Io; use Text_Io;
:
: procedure Foo is
:
: type Hex_Num is mod 16;
:
: function Hext (N : Integer) return Hex_Num is
: begin
: -- == (1+ (n mod 16)), which is the logic error.
                                           ^^^^^^^^^^^^ not really, see below
: return Hex_Num(1 + (N mod Hex_Num'Modulus));
: end Hext;
:
: begin
: for I in 0..20 loop
: Put_Line("Answer is: " & Hex_Num'Image(Hext(i)));
      Put_Line("Answer is: " & Integer'Image(Hext(i)));
: end loop;
: end;

In the Lisp example there was a "typo context". "next" should have
been where "hext" was actually typed in the Lisp example.
Therefore, an integer number was actually wanted ("next"), not
a hex number ("hext").
So there must be an Integer'image reflecting the logic/expectation
("next") not a Hex_Num'image (typo "hext").
The error is caught by the compiler.

    15. Put_Line("Answer is: " & Integer'Image(Hext(i)));
                                                     |
>>> expected type "Standard.Integer"
>>> found type "Hex_Num" defined at line 4

-- Georg

Relevant Pages

  • Re: ADA Popularity Discussion Request
    ... :> jayessay wrote: ... :> See below, there isn't a logic error, only a typo. ... talking about the logic error in the Hext function itself! ... :> been where "hext" was actually typed in the Lisp example ...
    (comp.lang.ada)
  • Re: ADA Popularity Discussion Request
    ... > by an incrementing human? ... > See below, there isn't a logic error, only a typo. ... The logic error is that Hext is broken ... > The error is caught by the compiler. ...
    (comp.lang.ada)