From: Per Bothner <per@bothner.com>
To: Jamison Hope <jrh@theptrgroup.com>,
"kawa@sourceware.org list" <kawa@sourceware.org>
Subject: Re: strange int->boolean behavior
Date: Thu, 19 Feb 2015 23:06:00 -0000 [thread overview]
Message-ID: <54E66BD2.1060903@bothner.com> (raw)
In-Reply-To: <72768B2F-733F-4F37-BB02-880E16C2E855@theptrgroup.com>
On 12/18/2014 10:19 AM, Jamison Hope wrote:
> Sometimes, a primitive 0 is false:
>
> #|kawa:1|# (->boolean (->int 3))
> Exception in thread "main" java.lang.Error: unsupported CodeAttr.emitConvert
> at gnu.bytecode.CodeAttr.emitConvert(CodeAttr.java:2006)
> [...]
>
> #|kawa:1|# (if (->int 3) "YES" "NO")
> YES
> #|kawa:2|# (if (->int 0) "YES" "NO")
> YES
> #|kawa:3|# (define (f x::int) ::string (if x "YES" "NO"))
> #|kawa:4|# (f 3)
> YES
> #|kawa:5|# (f 0)
> NO
> #|kawa:6|# (disassemble f)
> In class atInteractiveLevel$3
>
> Method name:"f" public static Signature: (int)java.lang.CharSequence
> Attribute "Code", length:70, max_stack:1, max_locals:1, code_length:14
> 0: iload_0
> 1: ifeq 10
> 4: getstatic <Field atInteractiveLevel$3.Lit0 java.lang.String>
> 7: goto 13
> 10: getstatic <Field atInteractiveLevel$3.Lit1 java.lang.String>
> 13: areturn
>
> I get similar results with the other primitive types. If I'm following things correctly,
>it's ConditionalTarget#compileFromStack which is treating zero as false?
Yes. I checked in a fix for this. The change in ConditionalTarget depends on the language;
specifically whether language.isTrue(Integer.valueOf(0)). If so, we an just
emitGoto the true label.
I forgot about or overlooking this message, but found it while searching for
another discussion (which turn out to be "proposed changes to handling of false
and end-of-list").
(I'm looking into doing at least part of that previous proposal - specifically
treating #!null as false.)
--
--Per Bothner
per@bothner.com http://per.bothner.com/
next prev parent reply other threads:[~2015-02-19 23:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-18 18:19 Jamison Hope
2015-02-19 23:06 ` Per Bothner [this message]
2015-02-20 0:39 ` Jamison Hope
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