29
Numerics library
[numerics]
29.5
Random number generation
[rand]
29.5.9
Random number distribution class templates
[rand.dist]
29.5.9.3
Bernoulli distributions
[rand.dist.bern]
29.5.9.3.2
Class template
binomial_
distribution
[rand.dist.bern.bin]
1
#
A
binomial_
distribution
random number distribution produces integer values
i
≥ 0
distributed according to the discrete probability function in Formula
29.5
.
P
(
i
|
t
,
p
)
=
(
t
i
)
⋅
p
i
⋅
(
1
−
p
)
t
−
i
(29.5)
🔗
namespace
std
{
template
<
class
IntType
=
int
>
class
binomial_distribution
{
public
:
// types
using
result_type
=
IntType;
using
param_type
=
unspecified
;
// constructors and reset functions
binomial_distribution
(
)
:
binomial_distribution
(
1
)
{
}
explicit
binomial_distribution
(
IntType t,
double
p
=
0.5
)
;
explicit
binomial_distribution
(
const
param_type
&
parm
)
;
void
reset
(
)
;
// equality operators
friend
bool
operator
=
=
(
const
binomial_distribution
&
x,
const
binomial_distribution
&
y
)
;
// generating functions
template
<
class
URBG
>
result_type
operator
(
)
(
URBG
&
g
)
;
template
<
class
URBG
>
result_type
operator
(
)
(
URBG
&
g,
const
param_type
&
parm
)
;
// property functions
IntType t
(
)
const
;
double
p
(
)
const
; param_type param
(
)
const
;
void
param
(
const
param_type
&
parm
)
; result_type min
(
)
const
; result_type max
(
)
const
;
// inserters and extractors
template
<
class
charT,
class
traits
>
friend
basic_ostream
<
charT, traits
>
&
operator
<
<
(
basic_ostream
<
charT, traits
>
&
os,
const
binomial_distribution
&
x
)
;
template
<
class
charT,
class
traits
>
friend
basic_istream
<
charT, traits
>
&
operator
>
>
(
basic_istream
<
charT, traits
>
&
is, binomial_distribution
&
x
)
;
}
;
}
🔗
explicit
binomial_distribution
(
IntType t,
double
p
=
0.5
)
;
2
#
Preconditions
:
0 ≤
p
≤ 1
and
0 ≤
t
.
3
#
Remarks
:
t
and
p
correspond to the respective parameters of the distribution
.
🔗
IntType t
(
)
const
;
4
#
Returns
: The value of the
t
parameter with which the object was constructed
.
🔗
double
p
(
)
const
;
5
#
Returns
: The value of the
p
parameter with which the object was constructed
.