Intrinsic procedures are functions and subroutines that are included in the Fortran 90 library. There are four classes of these intrinsic procedures, as follows:
These procedures have scalar dummy arguments that can be called with scalar or array actual arguments. There are many elemental intrinsic functions and one elemental intrinsic subroutine (MVBITS).
If the arguments are all scalar, the result is scalar. If an actual argument is array-valued, the intrinsic procedure is applied to each element of the actual argument, resulting in an array that has the same shape as the actual argument.
If there is more than one array-valued argument, they must all have the same shape.
These functions have results that depend on the properties of their principal argument, not the value of the argument (the argument value can be undefined).
These functions have one or more array-valued dummy or actual arguments, an array result, or both. The intrinsic function is not applied elementally to an array-valued actual argument; instead it changes (transforms) the argument array into another array.
These procedures must be called with only scalar arguments; they return scalar results. All subroutines (except MVBITS) are nonelemental.
Intrinsic procedures are invoked the same way as other procedures, and follow the same rules of argument association.
The intrinsic procedures have generic (or common) names, and many of the intrinsic functions have specific names. (Some intrinsic functions are both generic and specific.)
In general, generic functions accept arguments of more than one data type; the data type of the result is the same as that of the arguments in the function reference. For elemental functions with more than one argument, all arguments must be of the same type (except for the function MERGE).
When an intrinsic function is passed as an actual argument to a procedure, its specific name must be used, and when called, its arguments must be scalar. Not all specific intrinsic functions are allowed as actual arguments in all circumstances. Table 9-1 lists specific functions that cannot be passed as actual arguments.
| AIMAX0 | DREAL | INT2 | KMIN1 |
| AIMIN0 | EOF | INT4 | LGE |
| AJMAX0 | FLOAT | JFIX | LGT |
| AJMIN0 | FLOATI | JIDINT | LLE |
| AKMAX0 | FLOATJ | JIFIX | LLT |
| AKMIN0 | FLOATK | JINT | LOC |
| AMAX0 | ICHAR | JMAX0 | MALLOC |
| AMAX1 | IDINT | JMAX1 | MAX0 |
| AMIN0 | IFIX | JMIN0 | MAX1 |
| AMIN1 | IIDINT | JMIN1 | MIN0 |
| CHAR | IIFIX | KIDINT | MIN1 |
| DBLE | IINT | KIFIX | QEXT |
| DBLEQ | IMAX0 | KINT | QEXTD |
| DFLOTI | IMAX1 | KIQINT | QMAX1 |
| DFLOTJ | IMIN0 | KIQNNT | QMIN1 |
| DFLOTK | IMIN1 | KMAX0 | REAL |
| DMAX1 | INT | KMAX1 | SNGL |
| DMIN1 | INT1 | KMIN0 | SNGLQ |
This chapter contains information on the following topics: