Texas Instruments TI-92 Owners Manual - Page 115

Creating a MultiStatement Function Note: For information about similarities and differences between functions and programs, refer to Chapter 17. You can also create a user-defined function whose definition consists of multiple statements. The definition can include many of the control and decision-making structures (If, ElseIf, Return, etc.) used in programming. For example, suppose you want to create a function that sums a series of reciprocals based on an entered integer (n): 1 n + 1 nì 1 + ... + 1 1 Variables not in the argument list must be declared as local. Returns a message if nn is not an integer or if nn0. Sums the reciprocals. Returns the sum. When creating the definition of a multi-statement function, it may be helpful to visualize it first in a block form. Func Local temp,i If fPart(nn)ƒ0 or nn0 Return "bad argument" 0! temp For i,nn,1,ë 1 approx(temp+1/i)! temp EndFor Return temp EndFunc Func and EndFunc must begin and end the function. For information about the individual statements, refer to Appendix A. When entering a multi-statement function on the Home screen, you must enter the entire function on a single line. Use the Define command just as you would for a single-statement function. Use argument names that will never be used when calling the function or program. Use a colon to separate each statement. Define sumrecip(nn)=Func:Local temp,i: ... :EndFunc Tip: It's easier to create a complicated multi-statement function in the Program Editor than on the Home screen. Refer to Chapter 17. On the Home screen: Enter a multi-statement function on one line. Be sure to include colons. Multi-statement functions show as "Func". Evaluating a Function You can use a user-defined function just as you would any other function. Evaluate it by itself or include it in another expression. 98 Chapter 5: Additional Home Screen Topics