The following system variables contain pre-defined constants or values for use by IDL routines. System variables can be used just like other variables. For example, the command:
PRINT, ACOS(A) *
converts a result expressed in radians to one expressed in degrees.
A read-only variable containing the double-precision value of pi (p).
A read-only variable containing the floating-point value used to convert degrees to radians (p/180 @ 0.01745).
An array variable containing the information needed to effect coordinate conversions between points of latitude and longitude and map coordinates. The values in this array are established by the MAP_SET procedure; the user should not change them directly.
A read-only variable containing the single-precision value of pi (p).
A read-only variable containing the floating-point value used to convert radians to degrees (180/p @ 57.2958).
A read-only variable containing the IEEE single- and double-precision floating-point values Infinity and NaN (Not A Number).
!VALUES,4 tags, length=24: F_INFINITY FLOAT Infinity F_NAN FLOAT NaN D_INFINITY DOUBLE Infinity D_NAN DOUBLE NaN
where Infinity is the value Infinity and NaN is the value Not A Number. For more information on these special floating-point values, see Special Floating-Point Values.