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Re: strange int->boolean behavior
- From: Per Bothner <per at bothner dot com>
- To: Jamison Hope <jrh at theptrgroup dot com>, "kawa at sourceware dot org list" <kawa at sourceware dot org>
- Date: Thu, 19 Feb 2015 15:03:46 -0800
- Subject: Re: strange int->boolean behavior
- Authentication-results: sourceware.org; auth=none
- References: <72768B2F-733F-4F37-BB02-880E16C2E855 at theptrgroup dot 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/