# number_properties

determine floating-point parameters

### Syntax

pr = number_properties(prop)

### Arguments

- prop
string

- pr
real or boolean scalar

### Description

This function may be used to get the characteristic
numbers/properties of the floating point set denoted here by
`F(b,p,emin,emax)`

(usually the 64 bits float numbers set
prescribe by IEEE 754). Numbers of `F`

are of the
form:

`sign * m * b^e`

`e`

is the exponent and `m`

the
mantissa:

the digits are in `[0, b-1]`

and `e`

in `[emin, emax]`

, the number is
said "normalized" if
. The following queries may be used:

- prop = "radix"
then

`pr`

is the radix`b`

of the set`F`

- prop = "digits"
then

`pr`

is the number of digits`p`

- prop = "huge"
then

`pr`

is the max positive float of`F`

- prop = "tiny"
then

`pr`

is the min positive normalized float of`F`

- prop = "denorm"
then

`pr`

is a boolean (%t if denormalized numbers are used)- prop = "tiniest"
then if denorm = %t,

`pr`

is the min positive denormalized number else`pr`

= tiny- prop = "eps"
then

`pr`

is the epsilon machine ( generally ( ) which is the relative max error between a real`x`

(such than`|x|`

in`[tiny, huge]`

) and`fl(x)`

, its floating point approximation in`F`

- prop = "minexp"
then

`pr`

is`emin`

- prop = "maxexp"
then

`pr`

is`emax`

This function uses the lapack routine `dlamch` to get the machine
parameters (the names (radix, digit, huge, etc...) are those recommended by the LIA 1
standard and are different from the corresponding lapack's ones). |

Sometimes you can see the following definition for the epsilon machine :
but in this function we use the traditional one
(see prop = "eps" before) and so
if normal rounding occurs, and
otherwise. |

### Examples

b = number_properties("radix") eps = number_properties("eps")

## Comments

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