Subprograms › Linkage Conventions for CA Ideal Subprograms › Parameter Rules

Parameter Rules

The following rules apply to defining parameters in a CA Ideal subprogram:

• You must specify a parameter in the subprogram for each data item to pass. The parameter definitions must match the type of each data item.
• The following restrictions apply to specific attributes:
  • alphanumeric

    fixed length-If you are using dynamic matching, then the length must be equal to or greater than the actual passed data item. The Characters attribute specifies the maximum length of the data item. If the item length is less when passed, then the actual length is the length assigned to the parameter.

    If you are using identical matching, the length must be the same.

    variable length-If you are using dynamic matching with update intent, length must be equal to or greater than actual passed data item.

    If you are not using matching with update intent, whether dynamic or identical matching, length must be the same.

  • Numeric-If dynamic matching, the internal type is taken from the data item in the calling program. Digit values, if specified, for integer and decimal places on parameter must match data item. Otherwise, it is taken from data item.

    If you are using identical matching, internal type and digits values must match.

  • date-Same as numeric.
  • flag-No restrictions.
  • group name-The structures must be compatible using the tests for the MOVE BY POSITION command.
  • condition name-Although a passed group field can contain a condition name, it cannot be passed as an elementary data item.
  • occur value with DEP ON clause-If dynamic matching, the object of the DEP ON clause must match. The object is the field that determines the number of occurrences. If identical matching, the Occur and DEP ON clauses must match. The subscripted name of an occurrence is treated as an elementary data item.
  • occur value without DEP ON clause-If dynamic matching, value must be equal to or greater than data item. If the value specifies the maximum number occurrences, then the actual number passed is assigned to the parameter. If identical matching, the Occur and DEP ON clauses must match. The subscripted name of an occurrence is treated as an elementary data item.
  • Redefines-If not defined on the parameter, it is ignored. If specified on the parameter but not on the data item, a runtime error occurs.
  • Nullable fields (defined using WITH IND)-If passed by the calling program, it must be defined using WITH IND in the called subprogram.
• A panel passed as a group must be dynamic.
• A CA Ideal program cannot be called recursively; that is, a program cannot call itself or call a program that is already active in the current CA Ideal run-unit.
• A runtime error occurs if a CALL statement passes more data items than the number of level-1 parameters defined for the called subprogram. However, if a CALL statement passes fewer data items than the number of level-1 parameters defined for the called subprogram, no runtime error occurs unless the subprogram attempts to reference a parameter for which no data item was passed. Since parameters are passed and referenced positionally, you can omit parameters from the end of the CALL statement list without affecting the other parameters. You cannot omit values from the list. The $RECEIVED function can determine which level-1 parameters were actually passed.