hex2num can't recover value from the hex by num2hex

3 vues (au cours des 30 derniers jours)
david wang
david wang le 19 Déc 2019
Commenté : Walter Roberson le 21 Déc 2019
my matlab script
num2hex(single(-1.7783722e-1))
ans =
'be361af6'
and
hex2num('be361af6')
ans =
-5.146794990196213e-09
why I can not recover the original value ?

Réponse acceptée

Rik
Rik le 19 Déc 2019
As the documentation explains, hex2num assumes the hex is a representation of a double, while num2hex also supports the single data type. That means that despite the names, these two functions are not the exact mirror of each other.
It looks like you will have to implement hex2num yourself if you want to have a single as an output.
  1 commentaire
david wang
david wang le 21 Déc 2019
Rik: thanks for the answer and explanation !

Connectez-vous pour commenter.

Plus de réponses (1)

James Tursa
James Tursa le 19 Déc 2019
Try
typecast(uint32(hex2dec('be361af6')),'single')
  2 commentaires
david wang
david wang le 21 Déc 2019
it works. Thanks.
Walter Roberson
Walter Roberson le 21 Déc 2019
This will work for the case of single, but hex2dec() cannot substitute for hex2num() for the case where the input is representing double: for a lot of the important range, the decimal results produced by hex2num() would be outside what can be represented as double precision.
Instead of hex2dec, the form that is more generally usable is
sscanf(HEXSTRING, '%lx')
which gives back a uint64 that you can then typecast.
typecast(uint32(sscanf('be361af6', '%lx')),'single')
typecast(sscanf('400921fb54442d18', '%lx'), 'double')

Connectez-vous pour commenter.

Catégories

En savoir plus sur Data Type Conversion dans Help Center et File Exchange

Produits


Version

R2017b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by