The Icon language [was: Re: PEP 285: Adding a bool type]

[Steve Holden]

"Alex Martelli" <aleax at aleax.it> wrote in message
news:QPoq8.44596$pT1.1256392 at news1.tin.it...
> Chris Barker wrote:
>         ...
> > do think that that is how it should be in the ideal language. The
> > concept of True or False is distinct from the concept of a number, and
> > I'd like to see it stay that way in the language.
>
> Have a look at Icon (or Snobol, but that was goto-based... Icon's
> much nicer).  It CENTERS on this concept.
>
[...]
>
> If you want "booleans" given the respect you seem to think they
> deserve, you may actually be happier with Icon than with Python.
> Me, I think that Python's decision regarding "concrete nothings",
> although less pure, was more pragmatically useful than Icon's
> purity in distinguishing "something or nothing" from any actual
> kind of "somethings", and contributed to Python's greater success.
> But - study Icon, try it out on some concrete programming task,
> and make up your own mind.
>
Or take a look at this old program. Note especially the "/owid := 72" idiom,
used to default a variable, and the "every" construct, which forces a
context in which all values oif an expression are used. Icon was very
advanced for its time, but I don't think it really took the object-oriented
paradigm on board. Certainly the standard OO system was klugey, and never
became part of the language.

regards
 Steve

#
#    classify.icn:    read a mail file and produce a subject-sorted
#            list of mail items and replies, or an index to
#            the mail file.
#
#    (c) Copyright Steve Holden 1991
#
#    Identification:    @(#)classify.icn    1.2
#    SCCS source:    /export/home/steve/dev/tools/src/SCCS/s.classify.icn
#    Last change:    10:37:32    92/09/14
#    Retrieved on:    20:46:13    94/02/15
#
#    Bugs:        Sort is case-sensitive.
#            Craps out on overlength index lines.
#            (Possibly elsewhere) subjects are not always
#                well-trimmed.
#
#
link mlib                # mail i/o library

procedure main(arg)

while arg[1][1] == "-" do        # handle arguments
    case (o :=pop(arg))[2] of {
    "i":        indexrun := ""
    default:    stop("Unrecognised classify option: ",o)
    }

if *arg = 0 then arg := [ "-" ]
if *arg > 1 then stop("Bug: can only handle one file at a time. Sorry.")

ttls := table([])
refs := table([])

msg := []
while filename := pop(arg) do {
    ifn := OpenMail(filename) | stop("Cannot open file ",filename)
    while put(msg,ReadMail(ifn))
}

every m := 1 to *msg do {
    trim( \(msg[m].headers["Subject"][1]) | "** Untitled Mail" ) ?
        if (="Re:" & tab(upto(~':\t ')))
        then refs[ms := tab(0)] |||:= [m]
        else ttls[ms := tab(0)] |||:= [m]
}

tlst := sort(ttls)
rlst := sort(refs)


while (*tlst > 0) | (*rlst > 0) do {        # for each subject...
#    write("## ",*tlst,"+",*rlst)
    if (rlst[1][1] << tlst[1][1]) | (*tlst = 0)
    then {                    # orphaned reference
        subject := rlst[1][1]
        refs := pop(rlst)[2]
        ttls := []
    } else {                # message
        subject := tlst[1][1]
        ttls := pop(tlst)[2]
        if subject == rlst[1][1]    # handle references, if any
        then refs := pop(rlst)[2]
        else refs := []
    }
    if \indexrun then {
        present(subject,ttls,refs)
    } else
    every WriteMail(msg[!ttls | !refs])
}

end

procedure present(s, t, r, owid)

local    ts        # temp string for message numbers

/owid := 72
ts := ""
if *t > 0 then {
    every i := 1 to *t-1 do ts ||:= t[i] || ", "
    ts ||:= t[-1]
} else ts := "-"
if *r > 0 then {
    ts ||:= "; "
    every i := 1 to *r-1 do ts ||:= r[i] || ", "
    ts ||:= r[-1]
}
s ||:= repl(" ",3-(*s % 3))
write(s,right(ts,owid-*s,".. "))
return
end