SI
This function evaluates the sine integral.
Function Return Value
SI — Function value. (Output)
Required Arguments
X — Argument for which the function value is desired. (Input)
FORTRAN 90 Interface
Generic: SI (X)
Specific: The specific interface names are S_SI and D_SI.
FORTRAN 77 Interface
Single: SI (X)
Double: The double precision function name is DSI.
Description
The sine integral, Si(x), is defined to be
If
the answer is less accurate than half precision, while for x > 1 /ɛ, the answer has no precision. Here, ɛ = AMACH(4) is the machine precision.
Example
In this example, Si(1.25) is computed and printed.
 
USE SI_INT
USE UMACH_INT
 
IMPLICIT NONE
! Declare variables
INTEGER NOUT
REAL VALUE, X
! Compute
X = 1.25
VALUE = SI(X)
! Print the results
CALL UMACH (2, NOUT)
WRITE (NOUT,99999) X, VALUE
99999 FORMAT (' SI(', F6.3, ') = ', F6.3)
END
Output
 
SI( 1.250) = 1.146