HP Fortran Programmer's Reference (September 2007)

Intrinsic procedures
Intrinsic procedure specifications
Chapter 11 571
IRANP(X)
Description
Generate Poisson-distributed random numbers.
Class
Elemental nonstandard function.
Argument
X must be of REAL(4) type and must be in the range 0.0 through 87.33. For better
performance, it is recommended that X be less than 50.0 (see “Result value” below).
Result type/
type parameters
INTEGER(4) type.
Result value
IRANP returns an error code of -1 if X <= 0.0.
IRANP returns an error code of -2 if X > 87.33.
IRANP calculates exponentially distributed random numbers until the product is less than
exp(-X). The random number returned by IRANP is the number of exponentials needed,
minus 1. IRANP makes an average of X+1 calls to RAND, so it is recommended that X be less
than 50.
ISHFT(I, SHIFT)
Description
Performs a logical shift.
Class
Elemental function.
Arguments
I must be of type integer.