From: matz@ruby-lang.org
To: ruby-core@ruby-lang.org
Subject: [ruby-core:90978] [Ruby trunk Feature#15477] Proc#arity returns -1 for composed lambda Procs of known arguments
Date: Thu, 10 Jan 2019 08:04:30 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-76191.20190110080428.b16b45fdf63ba26c@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-15477.20181228052759@ruby-lang.org
Issue #15477 has been updated by matz (Yukihiro Matsumoto).
Yes, please.
Matz.
----------------------------------------
Feature #15477: Proc#arity returns -1 for composed lambda Procs of known arguments
https://bugs.ruby-lang.org/issues/15477#change-76191
* Author: robb (Robb Shecter)
* Status: Open
* Priority: Normal
* Assignee:
* Target version:
----------------------------------------
```
f = -> x { x + 2 }
g = -> x { x * 2 }
h = f << g
f.arity # => 1
g.arity # => 1
h.arity # => -1 THIS SHOULD BE 1 because h "knows" that it takes exactly 1 argument:
h.call # => ArgumentError (given 0, expected 1)
```
Lambda Procs which are composed using `<<` seem to partially lose knowledge of their arity. I don't know if this affects other procs, or the `>>` operator as well. The Proc#arity docs state that -1 is returned only when a variable or unknown number of arguments are expected by the Proc. But here, that's not the case.
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2019-01-10 8:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-15477.20181228052759@ruby-lang.org>
2018-12-28 5:28 ` [ruby-core:90767] [Ruby trunk Bug#15477] Proc#arity returns -1 for composed lambda Procs of known arguments robb+ruby
2019-01-01 11:09 ` [ruby-core:90842] [Ruby trunk Feature#15477] " mame
2019-01-10 8:04 ` matz [this message]
2019-03-15 12:39 ` [ruby-core:91849] " mathias
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