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From: Per Bothner <>
To: Duncan Mak <>,
	kawa mailing list <>
Subject: Re: Extending functional call syntax for Sequences to include Maps
Date: Fri, 3 Jul 2020 15:05:30 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 7/3/20 2:24 PM, Duncan Mak via Kawa wrote:
> More concisely, you can use (Kawa-specific) function call syntax:
> (vec1 3) ⇒ 8
> I was a little disappointed when I found out that this doesn't work for
> Maps, which is also something Clojure allows [0]:
> ;; This is Clojure not Scheme
> ({:age 42 :name "Joe"} :name)     ; ⇒ "Joe"
> ({:age 42 :name "Joe"} :age)      ; ⇒ 42
> ({:age 42 :name "Joe"} :unknown)  ; ⇒ nil

I vaguely remember discussing this some years ago, and I think the main
(conceptual) problem is how to handle arguments with no binding, i.e.
the 3rd case above.  By analogy with sequences, it should throw an
exception - which may not be the most convenient

I mentioned a couple of possible approaches, but I don't recall
what they were.  I think I was leaning towards a way to specify
a default value - and throw an exception when no default was specified.

I haven't been able to find that email, so far.

A possibly solution:

(htab key [default])

If there is no entry for key in htab, then default is returned
if specified; otherwise an exception is thrown.

You should also be able to do:

(set! (htab key) new-value)
	--Per Bothner

  reply	other threads:[~2020-07-03 22:05 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-03 21:24 Duncan Mak
2020-07-03 22:05 ` Per Bothner [this message]
2020-07-04  4:07   ` Duncan Mak
2020-07-15 18:44   ` Jamison Hope
2020-07-16  5:24     ` Per Bothner

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