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To be clear, I'm not working on this, was just thinking about it.<BR>
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- Jay<BR><BR> <BR>
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Subject: Re: [M3devel] TInt/TWord proposal (at least what I was thinking..)<BR>From: hosking@cs.purdue.edu<BR>Date: Thu, 11 Feb 2010 11:52:12 -0500<BR>CC: m3devel@elegosoft.com<BR>To: jay.krell@cornell.edu<BR><BR><BASE>
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<DIV><SPAN style="FONT-SIZE: medium" class=ecxApple-style-span><FONT class=ecxApple-style-span color=#0000ff face="'Gill Sans'">Steady on. I have it fixed. CHeckin coming. No need for more.</FONT></SPAN></DIV></SPAN></SPAN></SPAN></SPAN></SPAN></SPAN></SPAN></SPAN></DIV></SPAN></SPAN></DIV><BR>
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<DIV>On 11 Feb 2010, at 07:05, Jay K wrote:</DIV><BR class=ecxApple-interchange-newline>
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<DIV style="FONT-FAMILY: Verdana; FONT-SIZE: 10pt" class=ecxhmmessage>TInt/TWord proposal<BR> <BR><BR>TInt needs to be a "complete" replacement for INTEGER and LONGINT.<BR> Plus overflow checking.<BR> Not just for the frontend, but also m3back.<BR><BR> <BR>TWord needs to be a "complete" replacement for Word and Long.<BR> Therefore not likely any overflow checking.<BR><BR> <BR>But in reality you might need all four:<BR> signed with silent overflow<BR> signed with nonsilent overflow<BR> unsigned with silent overflow<BR> unsigned with nonsilent overflow<BR> <BR><BR>You can provide silent overflow by computing the result<BR>and leaving it to the caller to ignore the BOOLEAN or not.<BR> <BR><BR>However in practise I don't think I needed silent overflow at all.<BR>The only places I allow it, I think really I'm confusing TInt with TWord,<BR>because TWord doesn't provide the right interface.<BR> <BR> <BR>Settle on bits or bytes for sizes.<BR>Enshrine it mostly in the public interface.<BR> It maybe already is, granted.<BR> But more so -- external users can construct the things.<BR> <BR><BR>Operations with mixed sizes shall not be allowed. <=== *****<BR> Just as INTEGER, LONGINT, Word, Long don't allow.<BR> <BR> <BR>There would be some conversion functions, granted.<BR>SignedTruncate, UnsignedTruncate, SignExtend, ZeroExtend.<BR> <BR> <BR>Constants Zero, One, MOne, etc. shall probably be<BR>replaced with an array of 8 each, or maybe just<BR>1, 2, 4, 8 -- the number of bytes in the size.<BR> <BR><BR>"M" for "minus" is the wrong term.<BR>It should N or Neg or Negative.<BR><BR> <BR>Something like:<BR>TYPE BitCount = [8, 16, 32, 64]; (* not legal, darn *)<BR>TYPE ByteCount = [1, 2, 4, 8]; (* also not legal, darn *)<BR>TYPE ByteCount = [1..8]; (* wasteful, darn *)<BR><BR>CONST Invalid = Target.Int{-1,IntBytes{0,..}};<BR> <BR>CONST ZeroBytes = IntBytes{0,..};<BR>CONST OneBytes = IntBytes{1,0,..};<BR>CONST NegativeOneBytes = IntBytes{16_FF,..};<BR>CONST ThirtyTwoBytes = IntBytes{32,0,..};<BR>etc.<BR> <BR>CONST Zero = ARRAY ByteCount OF { Target.Int{1,ZeroBytes}, Target.Int{2,ZeroBytes}, Invalid, Target.Int{4,ZeroBytes}, Invalid, Invalid,<BR> Invalid, Target.Int{8,ZeroBytes}};<BR> <BR>CONST One = ARRAY ByteCount OF { Target.Int{1,OneBytes}, Target.Int{2,OneBytes}, Invalid, Target.Int{4,OneBytes}, Invalid, Invalid,<BR> Invalid, Target.Int{8,OneBytes}};<BR>etc.<BR><BR> <BR>TInt.Zero becomes replaced by, e.g. TInt.Zero[Target.Integer.bytes] or TInt.Zero[Target.Longint.bytes]<BR> <BR><BR>MAYBE as a possible simplification to the user:<BR><BR>Introduce InternalTInt which is today's TInt and then:<BR>TInt implies Target.Integer.bytes<BR>TWord implies Target.Integer.bytes<BR>new TLongint implies Target.Longint.bytes<BR>new TLong implies Target.Longint.bytes<BR> <BR><BR>I really thing the short name "Long" is bad.<BR>There is no indication of unsignedness in it.<BR>It should be ULong or UnsignedLong or LongWord.<BR><BR> <BR>"Word" is to INTEGER as what is to LONGINT?<BR> I don't think Long is the answer.<BR>I'll start another thread on this.<BR> <BR> <BR>m3back maintains a stack of mixed types, but I think it works out ok.<BR> <BR> <BR>All that being said, I think what is there works and isn't terrible<BR>and we don't need to solve lots of problems here.<BR> <BR> <BR>I do think the variable sizing is a bit of a problem though.<BR> <BR> <BR> - Jay<BR><BR></DIV></SPAN></BLOCKQUOTE></DIV><BR> </body>
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