RE: Re: converting hex strings

*To*: mathgroup at smc.vnet.net*Subject*: [mg27479] RE: [mg27456] Re: converting hex strings*From*: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.de>*Date*: Tue, 27 Feb 2001 00:37:32 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

for my comment see below -----Original Message----- From: Allan Hayes [mailto:hay at haystack.demon.co.uk] To: mathgroup at smc.vnet.net Subject: [mg27479] [mg27456] Re: converting hex strings Maarten, ToExpression["16^^"<>#]&/@{"01a0","ffe","0080"} {416,4094,128} You have one f too many. -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 <maarten.vanderburgt at icos.be> wrote in message news:97a7b2$aks at smc.vnet.net... > Hallo, > > I have a list of hexadecimal strings (read from a hex string text file): > e.g. {"01a0", "fffe", "0080"} representing integers. > How can I convert such a list to integers so that I get {416, 4094, 128}? > I cannot make a function using something like > > hextoint = 16^^#& > > or > > hextoin = 16^^ToExpression[#]& > > I get errors like below: > > In[44]:= hexstr = "a1b0" > t = ToExpression[hexstr]; > 16^^t > General::"digit": "Digit at position \!\(1\) in \!\(\"t\"\) is too large to > \ > be used in base \!\(16\)." > > Where does this error come from? > > While this works ok: > In[43]:= 16^^a1b0 > Out[43]= 41392 > > The ToExpression[ ] also would give problems: ToExpression["01a0"] returns > 0. > > Has anyone done anything along these lines? > > How would I have to convert a hex list representing floats (IEEE floating > point standard)?, e.g. {"42c8000", "3dfcd35b", "bf80000"} which should > convert to {100.0, 0.12345, -1.0} in a decimal notation. > > Thanks for your help > > Maarten > > ------------------------------------------- > Maarten van der Burgt > > Icos Vision Systems > Esperantolaan 9 > B-3001 Leuven > Belgium > ------------------------------------------- > > > -------------------- [Hartmut Wolf] Maarten, as you see from In[17]:= 16^^a1b0 // BoxForm Out[17]= "41392" (the output is a string!) ^^ is a evaluated when parsing the textual input, it is not a Mathematica function (hasn't even got a name). Conversion from text may be called by ToExpression, so Allan's form follows. As for the IEEE floating point standard I recommend to visit http://www.psc.edu/general/software/packages/ieee/ieee.html For that we first need a binary representation In[36]:= HexToBinDigits = (IntegerDigits[#, 2, 32] &) /@ (ToExpression["16^^" <> #] &) In[37]:= (exa = HexToBinDigits /@ {"42c80000", "3dfcd35b", "bf800000"}) // TableForm[#, TableSpacing -> {1, 0}] & compare that with In[38]:= BaseForm[#, 2] & /@ (ToExpression["16^^" <> #] &) /@ {"42c80000", "3dfcd35b", "bf800000"} // TableForm[#, TableAlignments -> Right] & We now may implement what we have learnt from psc.edu: In[39]:= FromIEEE32Digits[nn_] := With[{s = First[nn], e = FromDigits[Take[nn, {2, 9}], 2], f = FromDigits[Drop[nn, 9], 2]}, Which[e == 255 && f != 0, NaN, e == 255 && f == 0 && s == 1, -Infinity, e == 255 && f == 0 && s == 0, Infinity, 0 < e < 255, (-1)^s*2^(e - 127)* (1.`7.22472 + N[f/2^23, 7.22472]), e == 0 && f != 0, ((-1)^s*(0 + N[f/2^23, 7.22472]))/2^126, e == 0 && f == 0 && s == 1, -zero, e == 0 && f == 0 && s == 0, 0]] As you see it is not quite possible to truely implement the IEEE 32 bit Standard with Mathematica. You now may try the examples from the web page cited, and also your's: In[56]:= FromIEEE32Digits /@ exa Out[56]= {100., 0.12345, -1.} -- Hartmut