Tasks with Parameters

The following is an example of a task with a parameter. This task calculates the square of a number and outputs its value on the terminal.

      SUBROUTINE SQUARE(STATUS)
      INTEGER STATUS
      REAL R,RR
      CALL PAR_GET0R('VALUE',R,STATUS)
      RR = R*R           
      CALL MSG_SETR('RVAL',R)
      CALL MSG_SETR('RSQUARED',RR)
      CALL MSG_OUT(' ','The Square of ^RVAL is ^RSQUARED',STATUS)
      END

This program uses the subroutine PAR_GET0R to get the value of the parameter VALUE (there are similar routines for other types). Output of the numbers is done using the routine MSG_SETR to give values to the tokens RVAL and RSQUARED which are then inserted into the MSG_OUT output string using the ^RVAL notation. The interface file for this example is given below.

  INTERFACE SQUARE
 
    PARAMETER VALUE
      TYPE _REAL
      POSITION 1
      VPATH PROMPT
      PPATH CURRENT
      PROMPT 'Number to be squared'
    ENDPARAMETER

  ENDINTERFACE

The interface file has an entry for the parameter VALUE. The TYPE field specifies the type of the parameter. The underscore prefix on '_REAL' identifies it as a primitive type (i.e. a simple number or string, rather than an HDS structure or Device name). The position field specifies the position that the parameter is expected in if it appears on the command line.

The VPATH entry specifies how the parameter value is to be obtained if it not found on the command line. In this case it is to be prompted for. The PPATH entry specifies how the default value that appears in the parameter prompt is to be obtained. In this case the CURRENT value (i.e. the value the parameter had at the end of the last execution of the command) is used. The PROMPT field gives the prompt string to be used.

Interface files are described in more detail in SUN/115.

To run this example we would compile and link it as described above and then use the following ICL commands:

    ICL> DEFINE SQUARE SQUARE
    ICL> SQUARE 12
    Loading SQUARE into 03BCSQUARE
    The Square of 12 is 144
    ICL> SQUARE (SQRT(3))
    The Square of 1.73205 is 3
    ICL> SQUARE
    VALUE - Number to be squared /0.173205E+01/ > 7
    The Square of 7 is 49
    ICL>