Texas Instruments PLUS TI-89 - Manual (Page 496)

Appendix A: Functions and Instructions 479
8992APPA.DOC TI-89 / TI-92 Plus: Appendix A (US English) Susan Gullord Revised: 02/23/01 1:48 PM Printed: 02/23/01 2:21 PM Page 479 of 132
The example Program Editor function to the
right uses
getType() and part() to partially
implement symbolic differentiation. Studying
and completing this function can help teach
you how to differentiate manually. You could
even include functions that the
TI
-89 / TI-92 Plus cannot differentiate, such
as Bessel functions.
:d(y,x)
:Func
:Local f
:If getType(y)="VAR"
: Return when(y=x,1,0,0)
:If part(y)=0
: Return 0 ¦
y= p,ˆ,i,numbers
:part(y,0)! f
:If f=" L" ¦ if negate
: Return ë d(part(y,1),x)
:If f=" − " ¦ if minus
: Return d(part(y,1),x)
ì d(part(y,2),x)
:If f="+"
: Return d(part(y,1),x)
+d(part(y,2),x)
:If f="ù "
: Return
part(y,1)ù d(part(y,2),x)
+part(y,2)ù d(part(y,1),x)
:If f="{"
: Return seq(d(part(y,k),x),
k,1,part(y))
:Return undef
:EndFunc
PassErr CATALOG
PassErr
Passes an error to the next level.
If “errornum” is zero, PassErr does not do
anything.
The Else clause in the program should use
ClrErr or PassErr . If the error is to be
processed or ignored, use ClrErr . If what to
do with the error is not known, use PassErr
to send it to the next error handler. (See also
ClrErr .)
See ClrErr program listing example.
Pause CATALOG
Pause [ expression ]
Suspends program execution. If you include
expression , displays expression on the Program
I/O screen.
expression can include conversion operations
such as 4 DD and 4 Rect . You can also use the 4
operator to perform unit and number base
conversions.
If the result of expression is too big to fit on a
single screen, you can use the cursor pad to
scroll the display.
Program execution resumes when you
press ¸.
Program segment:
©
:ClrIO
:DelVar temp
:1
"temp[1]
:1 "temp[2]
:Disp temp[2]
:¦
Guess the Pattern
:For i,3,20
: temp[iì2]+temp[iì1]
"temp[i]
: Disp temp[i]
: Disp temp,"Can you guess the
next","number?"
: Pause
:EndFor
©