Target Language Compiler

Target Language Functions

The target language function construct is

• %function identifier ( optional-arguments ) [Output | void]
  %return
  %endfunction
  

Functions in the target language are recursive and have their own local variable space. Target language functions do not produce any output, unless they explicitly use the %openfile, %selectfile, and %closefile directives, or are output functions.

A function optionally returns a value with the %return directive. The returned value can be any of the types defined in Table 6-2, Target Language Values.

In this example, a function, name, returns x, if x and y are equal, and returns z, if x and y are not equal:

• %function name(x,y,z) void
  
  %if x == y
     %return x
  %else
     %return z
  %endif
  
  %endfunction
  

Function calls can appear in any context where variables are allowed.

All %with statements that are in effect when a function is called are available to the function. Calls to other functions do not include the local scope of the function, but do include any %with statements appearing within the function.

Assignments to variables within a function always create new, local variables and can not change the value of global variables unless you use the scope resolution operator (::).

By default, a function returns a value and does not produce any output. You can override this behavior by specifying the Output and void modifiers on the function declaration line, as in

• %function foo() Output
  ...
  %endfunction
  

In this case, the function continues to produce output to the currently open file, if any, and is not required to return a value. You can use the void modifier to indicate that the function does not return a value, and should not produce any output, as in

• %function foo() void
  ...
  %endfunction
  

Variable Scoping Within Functions

Within a function, the left-hand member of any %assign statement defaults to create a local variable. A new entry is created in the function's block within the scope chain; it does not affect any of the other entries. An example is shown in Figure 6-2.

You can override this default behavior by using %assign with the scope resolution operator (::).

When you introduce new scopes within a function using %with, these new scopes are used during nested function calls, but the local scope for the function is not searched. Also, if a %with is included within a function, its associated scope is carried with any nested function call, as shown in Figure 6-5, Scoping Rules When Using %with Within a Function,.

Figure 6-5: Scoping Rules When Using %with Within a Function

%return

The %return statement closes all %with statements appearing within the current function. In this example, the %with statement is automatically closed when the %return statement is encountered, removing the scope from the list of searched scopes:

• %function foo(s)
      %with s
          %return(name)
      %endwith
  %endfunction
  

The %return statement does not require a value. You can use %return to return from a function with no return value.

Variable Scoping

Command Line Arguments