1d3 = 1e3 = 1000? in matlab

Hi everyone!

I want know what's difference between 'd' and 'e' in matlab.

Sincerely, JH Jung

Answer 1

[Walter Roberson]

Historical support. I don't think the "d" form is even documented now. The "D" form was common in FORTRAN in the 1960's.

[JiHun Jung]

Walter Roberson, Thank for your answer!

Answer 2

[Jan]

Last year the technical support answered, that the following number formats are working, but not documented:

   2.
   .2
   .2e3
   .2e+03
   -.2E3
   2d3
   .2e2.*2.
   2..*.2

[JiHun Jung]

Jan Simon, Thank for your answer!

[Yukteshwar Baranwal]

@Jan @ So whether I use "e" or "d" both are same? Also, are both related to double precision?

[John D'Errico]

Yes. Either is fine. You always get the same result, a double precision number. d and e are essentially synonyms. They go back to long ago, to the roots of MATLAB, when Fortran allowed both forms for numbers. Even in Fortran they were essentially synonyms.

I would stick with e however, avoiding the d syntax. Undocumented features can sometime disappear in later releases. So sometime in the deep future, when all of us old people who remember what d does are dead and gone, they might decide to make things simpler and just remove support for a feature that nobody needs anyway.

[Walter Roberson]

FORTRAN E format was (originally) single precision for constants and D format was double precision. For example

COMMON/ABC/3.2e-1,3.2d-1/

initialized a single precision followed by a double precision

[Jan]

@Yukteshwar Baranwal: As I have written in my answer, I've asked the support, because I did not find an explanation in the documentation, if the mentiones notations are accepted.

Tme MathWorks answered, that only the formats are guaranteed to work, which are created as output of sprintf(). Therefore I do not use leading or trailing dots in numerical constants and stay at "e" or "E" for the exponent.

Nevertheless, fscanf accepts these notations and M-code is interpreted correctly also. But I stay at the documented syntax, because this is no drawback.