Programming Statements

Functions are special modules that return a single value. To write a function module, include a RETURN statement that specifies the value to return. The RETURN statement is necessary for a module to be a function. You can use a function module in an assignment statement, as you would a built-in function.

The symbol-table logic described in the preceding section also applies to function modules. In the following function module, the value of c in the local symbol table is assigned to the symbol z at main scope:

proc iml;
a = 10;
b = 20;
c = 30;
start Mod3(x,y);
   c = 2#x + y;
   return (c);            /* return function value */
finish Mod3;

z = Mod3(a,b);            /* call function         */
print a b c z;

Notice the following about this example:

Again notice that, inside the module, the symbols a, b, and z do not exist. Outside the module, the symbols x and y do not exist.

In the next example, you define your own function module, Add, which adds its two arguments:

proc iml;
start Add(x,y);
   sum = x+y;
   return(sum);
finish;

a = {9 2, 5 7};
b = {1 6, 8 10};
c = Add(a,b);
print c;

Function modules can also be called as arguments to other modules or to built-in functions. For example, in the following statements, the Add module is called twice, and the results from those calls are used as arguments to call the Add module a third time:

d = Add(Add({1 2},{3 4}), Add({5 6}, {7 8}));
print d;

Functions are resolved in the following order:

Because of this order of resolution, it is an error to try to define a function module that has the same name as a SAS/IML built-in function.