Pass-by-value parameters

When an argument has a data type that can fit into an MI_DATUM structure, the routine manager passes the argument by value. For these pass-by-value arguments, you declare a parameter as the actual parameter data type in the C-function declaration.

Types of values that fit in an MI_DATUM structure (Passed by value) lists data types for arguments that you can pass by value.

The following code fragment shows the bigger_int() UDR, which compares two mi_integer values. Because the routine manager passes mi_integer values by value, the UDR declares the two parameters with the mi_integer data type, not as pointers to mi_integer.
Figure 1. Passing arguments by value
mi_integer bigger_int(left, right)
   mi_integer left, right;
{
   if ( left > right )
      return(left);
   else
      return(right);
}
Any C-language code that calls bigger_int() must also pass the mi_integer values by value, as in the following sample call: 
mi_integer int1, int2, result;
...
int1 = 6;
in2 = 8;
result = bigger_int(int1, int2);