From: Isaac Gouy <igouy@...>
Date: 2005-09-23T06:56:43+09:00
Subject: Re: Large Ruby Apps ?

Ara.T.Howard@noaa.gov wrote:
> On Thu, 22 Sep 2005, Isaac Gouy wrote:
>
> > Ara.T.Howard wrote:
> > -snip-
> >> line one is an error.
> >> line two core dumps.
> >> line three will hang your machine.
> >
> > Humbly suggest that C is not the poster child for static type checking
> > :-)
> > iirc C is not even considered to be type safe.
>
> c is 100% staticly typed.  no exception.  static typing means types are know
> at compile type are cannot be changed via that execution path.  note that this
> is not the same as weak typing.  c is also weakly typed - meaning that the
> programmer can change the type of an expression (cast).  note that doing so is
> a __compile_time__ operation and cannot be done at run time so, even though
> you can write this
>
>    fprintf ("%s", (char *) 42);
>
> and abuse the absence of string typing (arguments to methods cannot be given
> the wrong type) the compiler still knows this __before__ your code execute and
> is, therefore know statically.
>
> c is not a poster child for strong typing - while, ironically, ruby is.
>
>    c      : static/weak type
>    c++    : static/weak type
>    ocaml  : static/strong type
>    java   : static/strong type
>    perl   : dynamic/weak type
>    ruby   : dynamic/strong type
>    python : dynamic/strong type
>
>
> only the combination of static and strong typing can allow a compiler to ensure
> program correctness.  note, however, that it's impossible to do any generic
> programming without also having a type inference system (a la ocaml) or code
> generation system (a la c++).  eg, if c were static and strongly typed you
> could not write
>
>    int pthread_create (pthread_t * thread, pthread_attr_t * attr,
>                        void *(*start_routine) (void *), void *arg);
> and i c++ you could not write
>
>    int foo (BaseClass *obj);
>
> unless you did so using templates.
>
> only with a system that is both strongly typed, statically typed, and uses
> type inference could you write something like
>
>      let rec sort = function
>        | [] -> []
>        | x :: l -> insert x (sort l)
>
>      and insert elem = function
>        | [] -> [elem]
>        | x :: l ->
>          if elem < x then elem :: x :: l else x :: insert elem l;;
>
>
>      sort [2; 1; 0];;
>      - : int list = [0; 1; 2]
>
>      sort ["yes"; "ok"; "sure"; "ya"; "yep"];;
>      - : string list = ["ok"; "sure"; "ya"; "yep"; "yes"]
>
> and have the compiler verify that it is correct and wil not core dump, etc.
> without writing, by hand, a duplicate method for all possible type - which is
> what c++ templates effectively do, though making a program verifiably correct
> would require their use exclusively and removal of type promotion rules, among
> other things.
>

C is not type safe; Smalltalk is type safe, afaik Ruby is type safe.

"So what is "strong typing"? ... If someone uses this phrase, be
sure to ask them to define it for you. (For amusement, watch them
squirm.)"

p271 "Programming Languages: Application and Interpretation"
http://www.cs.brown.edu/~sk/Publications/Books/ProgLangs/



> strangely noone suggests that c++ or java are not feasbile for large project
> and advocate ocaml instead.
>
> i really think this is more of a paradigm issue that any real issue.
>
> > The OP was unhelpfully vague about what he considered to be large
> > programs but imo 25,000 lines of java equivalent doesn't seem at all
> > large.
>
> but it makes me sick just thinking about it.  no program should be that big

Should we just ignore big problems? (Do we really need fly-by-wire and
derivatives trading?)


> -
> just like no soda should be 64 ounces.
>
> > The OP also mentioned "programming in the large" which perhaps implies
> > co-ordinating multi-person development.
>
> and weeks of memory leak debugging.
>
> i'm just kidding on those last two. ;-)
>
> cheers.
>
> -a
> --
> ===============================================================================
> | email :: ara [dot] t [dot] howard [at] noaa [dot] gov
> | phone :: 303.497.6469
> | Your life dwells amoung the causes of death
> | Like a lamp standing in a strong breeze.  --Nagarjuna
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