Intrinsic Procedures

 

Some tasks in a language are performed frequently, Fortran 90 has efficient implementations of such common tasks built-in to the language, these procedures are called intrinsic procedures. Fortran 90 has 113 intrinsic procedures in a number of different classes,

• elemental such as:
  • mathematical, such as, trigonometric and logarithms, for example, SIN or LOG.
  • numeric, for example, SUM or CEILING.
  • character, for example, INDEX and TRIM.
  • bit manipulation, for example, IAND and IOR.

  Elemental procedures apply to scalar objects as well as arrays -- when an array argument is supplied the same function is applied to each element of the array at (conceptually) the same time.

• inquiry, for example, ALLOCATED and SIZE; These report on the status of a program. We can inquire about:
  • the status of dynamic objects.
  • array bounds, shape and size.
  • kind parameters of an object and available kind representations, (useful for portable code).
  • the numerical model; used to represent types and kinds.
  • argument presence (for use with OPTIONAL dummy arguments).

• transformational, for example, REAL and TRANSPOSE. The functionality includes:
  • repeat (for characters -- repeats strings).
  • mathematical reduction procedures, ie, given an array return an object of less rank.
  • array manipulation -- shift operations, RESHAPE, PACK.
  • type coercion, TRANSFER copies bit-for-bit to an object of a different type. (Stops people doing dirty tricks like changing the type of an object across a procedure boundary which was a popular FORTRAN 77 `trick'.)
  • PRODUCT and DOT_PRODUCT (arrays).

• miscellaneous (non-elemental SUBROUTINE s) including timing routines, for example, SYSTEM_CLOCK and DATE_AND_TIME.

The procedures vary in what arguments are permitted. Some procedures can be applied to scalars and arrays, some to only scalars and some to only arrays. All intrinsics which take REAL valued arguments also accept DOUBLE PRECISION arguments.

• Type Conversion Functions
• Mathematical Intrinsic Functions
• Numeric Intrinsic Functions