NAME

nan$, dnan$, cnan$, znan$, cdnan$ - generate IEEE signalling Not-a-Number bit patterns

SYNOPSIS

real∗4 r
double precision d
complex∗8 c
double complex z(5), z0

data r / nan$() /, z / 5 ∗ znan$() /

d = dnan$()
c = cnan$()
z0 = cdnan$()

DESCRIPTION

nan$, dnan$, cnan$ and znan$ are constant intrinsics generating IEEE signalling Not-a-Number (NaN) bit patterns in single precision, double precision, single precision complex (real and imaginary portions each contain NaN) and double precision complex formats, respectively.  A constant intrinsic is a special hf77 intrinsic which produces, at compile time, a constant that may be otherwise difficult or impossible to represent using conventional constant syntax. 

These intrinsics may be used to initialize real and complex variables (via initialization statements or assignments) to values which are invalid if used in arithmetic operations, allowing users to quickly detect uses of otherwise uninitialized variables.  The Diagnostics section of the hf77(1) man page contains further information on tracking down NaN exceptions, whether generated from executable code or from within hf77 itself.

cdnan$ is identical to znan$. 

CAUTIONS

These intrinsics are all specific representations; there is no "generic" feature available.  The intrinsic appropriate to the data type of the receiving variable must be used. 

SEE ALSO

hf77(1). 

CX/UX Hf77 Fortran Reference Manual