Programming. Texas Instruments TI-NSPIRE CAS, TI-Nspire CX, TI-nspire CX CAS, TI-Nspire

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Annonce

Programming

You can create user-defined functions or programs by typing definition statements on the Calculator entry line or by using the Program Editor.

The Program Editor offers some advantages, and it is covered in this section. For information on defining programs and functions in

Calculator, see the “Calculator” chapter.

Overview of the Program Editor

The Program Editor helps you define, edit, and manage user-defined functions and programs.

• The editor has programming templates and dialog boxes to help you define functions and programs using correct syntax.

• The editor lets you enter multiple-line programming statements without requiring a special key sequence to add each line.

• You can easily create private and public library objects (variables, functions, and programs). For details, see the “Libraries” chapter.

• The editor is accessible from the main

Insert

menu as well as from the

Calculator’s

Functions & Programs

menu.

Program Editor menu – This menu is available anytime you are in the

Program Editor work area using the Normal view mode. On the handheld, press b

to display the menu.

Programming 673

Program Editor work area

Status line shows line number information and the name of the function or program being edited. An asterisk (*) indicates that this function is “dirty,” which means that it has changed since the last time its syntax has been checked and it has been stored.

Program Editor menu

Actions

New

Open

Import

View

Create Copy

Rename

Displays a dialog box for defining a new function or program.

Lets you open an existing library function or program for editing.

Imports a program or function from a library.

Lets you view (and optionally, edit) an existing library function or program.

Lets you copy the current function or program.

Lets you rename the current function or program.

Change Library Access Lets you change the access level of a library object to private (LibPriv), public

(LibPub), or none.

Insert Comment

Find

Inserts a comment (

) at the cursor position.

Displays a dialog box for text search.

Find and Replace

Go to Line

Go Back

Lets you find and, optionally, replace occurrences of specified text.

Moves the cursor to a specified line number.

Lets you easily return from the Program

Editor to the Calculator or Notes application after a runtime error occurs.

Close Closes the current function or program.

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Check Syntax &

Store

Check Syntax & Store Finds syntax errors and tries to put the cursor near the first error. If no errors, stores current function or program.

Check Syntax Finds syntax errors and tries to put the cursor near the first error.

Define Variables

Local

Define

Delete Variable

Func...EndFunc

Prgm...EndPrgm

Lock

Inserts

Local

Inserts

Define

Inserts

DelVar

Inserts

Func...EndFunc

template.

Inserts

Prgm...EndPrgm

template.

Inserts

Lock

unLock

, or

getLockInfo()

Control

If Inserts

statement.

If...Then...EndIf

Inserts

If...Then...EndIf

template.

If...Then...Else...EndIf

Inserts

If...Then...Else...EndIf

template.

ElseIf...Then

For...EndFor

While...EndWhile

Loop...EndLoop

Inserts

ElseIf...Then

For...EndFor

template.

Inserts

While...EndWhile

template.

Inserts

Loop...EndLoop

template.

Try...Else...EndTry

ClrErr

PassErr

Inserts

Try...Else...EndTry

template.

Inserts

ClrErr

Inserts

PassErr

Programming 675

Control

Inserts variable name .

Inserts

()

Transfer

Return

Cycle

Exit

Lbl

Go to Lbl

Stop

Input/Output

Disp

Inserts

return()

Cycle

Inserts

Exit

Stop

Inserts

Lbl

(label).

Inserts

Goto

Inserts the

Disp

(display) command.

Inserts the command.

Mode

Display Digits

Angle

Exponential Format

Real or Complex

Auto or Approx

Lets you select from several Float and Fix settings.

Lets you select Degrees, Radians, or

Gradians.

Lets you select Normal, Scientific, or

Engineering.

Lets you select Real, Rectangular, or Polar.

CAS: Lets you select Auto, Approximate, or Exact results.

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Mode

Vector Format

Base

CAS: Unit System

GetMode

Get Language Info

Lets you select Rectangular, Cylindrical, or

Spherical.

Lets you select Decimal, Hex, or Binary.

Lets you select SI or Eng/US.

Inserts

getMode()

Inserts

getLangInfo()

Defining a program or function

Starting a new Program Editor

1. To start the editor from a Calculator page,

– From the

Insert

menu, select

Program Editor

, and select

New

Handheld: Press b 9 1 1

2. To start the editor when not on a Calculator page,

– From the

Insert

menu, select

Program Editor

, and select

New

Handheld: Press

/ b 4 8 1

3. Type a name for the function or program you are defining.

4. Select the

Type

(

Program

Function

5. Set the

Library Access

– To use the function or program only from the current document and problem, select

None

– To make the function or program accessible from any document but not visible in the Catalog, select

LibPriv

Programming 677

– To make the function or program accessible from any document and also visible in the Catalog, select

LibPub (Show in Catalog)

For details, see the “Libraries” chapter.

6. Click

A new instance of the Program Editor opens, with a template matching the selections you made.

Entering lines into a function or program

The Program Editor does not execute the commands or evaluate expressions as you enter them. They are executed only when you evaluate the function or run the program.

1. If your function or program will require the user to supply arguments, type parameter names in the parentheses that follow the name.

Separate parameters with a comma.

2. Between the Func and EndFunc (or Prgm and EndPrgm) lines, enter the lines of statements that make up your function or program.

– You can either type the names of functions and commands or insert them from the Catalog.

– A line can be longer than the width of the screen; if so, you might have to scroll to view the entire statement.

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– After typing each line, press

. This inserts a new blank line and lets you continue entering another line.

– Use the

, and

arrow keys to scroll through the function or program for entering or editing commands.

Inserting comments

A comment symbol (©) lets you enter a remark. Comments can be useful to someone viewing or editing the program. Comments do not display when the program runs, and they have no effect on program flow.

Define LibPub volcyl(ht,r) =

Prgm

©volcyl(ht,r) => volume of cylinder

Disp “Volume =”, approx(

p ¦

r

ht)

©This is another comment.

EndPrgm

Comment showing required syntax. Because this library object is public and this comment is the first line in a Func or Prgm block, the comment displays in the Catalog as help. For details, see the

“Libraries” chapter.

To insert a comment:

1. Position the cursor at the end of the line where you want to insert a comment.

2. From the

Actions

menu, select

Insert Comment

3. Type the text of the comment after the © symbol.

Checking syntax

The Program Editor lets you check the function or program for correct syntax.

` From the

Check Syntax & Store

menu, select

Check Syntax

If the syntax checker finds any syntax errors, it displays an error message and tries to position the cursor near the first error so you can correct it.

Programming 679

Storing the function or program

You must store your function or program to make it accessible. The

Program Editor automatically checks the syntax before storing.

An asterisk (*) is displayed in the upper left corner of the Program Editor to indicate that the function or program has not been stored.

` From the

Check Syntax & Store

menu, select

Check Syntax & Store

If the syntax checker finds any syntax errors, it displays an error message and tries to position the cursor near the first error.

If no syntax errors are found, the message “Stored successfully“ is displayed in the status line at the top of the Program Editor.

Note: If the function or program is defined as a library object, you must also save the document in the designated library folder and refresh libraries to make the object accessible to other documents. For details, see the “Libraries” chapter.

Viewing a program or function

1. From the

Actions

menu, select

View

2. If the function or program is a library object, select its library from the

Location

list.

3. Select the function or program name from the

Name

list.

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The function or program displays in a viewer.

4. Use the arrow keys to view the function or program.

5. If you want to edit the program, click

Edit

Note: The

Edit

selection is available only for functions and programs defined in the current problem. To edit a library object, you must first open its library document.

Opening a function or program for editing

You can open a function or program from the current problem only.

Note: You cannot modify a locked program or function. To unlock the object, go to a Calculator page and use the

unLock

command.

1. Display the list of available functions and programs.

– From the

Actions

menu, select

Open

2. Select the item to open.

Importing a program from a library

You can import a function or program defined as a library object into a

Program Editor within the current problem. The imported copy is not locked, even if the original is locked.

1. From the

Actions

menu, select

Import

Programming 681

2. Select the

Library Name

3. Select the

Name

of the object.

4. If you want the imported object to have a different name, type the name under

Import As

Creating a copy of a function or program

When creating a new function or program, you might find it easier to start with a copy of the current one. The copy that you create is not locked, even if the original is locked.

1. From the

Actions

menu, select

Create Copy

2. Type a new name, or click

to accept the proposed name.

3. If you want to change the access level, select

Library Access

, and select a new level.

Renaming a program or function

You can rename and (optionally) change the access level of the current function or program.

1. From the

Actions

menu, select

Rename

2. Type a new name, or click

to accept the proposed name.

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3. If you want to change the access level, select

Library Access

, and select a new level.

Changing the library access level

1. From the

Actions

menu, select

Change Library Access

2. Select the

Library Access

– To use the function or program only from the current Calculator problem, select

None

– To make function or program accessible from any document but not visible in the Catalog, select

LibPriv

– To make the function or program accessible from any document and also visible in the Catalog, select

LibPub

Finding text

1. From the

Actions

menu, select

Find

2. Type the text that you want to find, and click

– If the text is found, it is highlighted in the program.

– If the text is not found, a notification message displays.

Finding and replacing text

1. From the

Actions

menu, select

Find and Replace

Programming 683

2. Type the text that you want to find.

3. Type the replacement text.

4. Click

Replace

to replace the first occurrence after the cursor position, or click

Replace All

to replace every occurrence.

Note: If the text is found in a math template, a message is displayed to warn you that your replacement text will replace the whole template—not just the found text.

Closing the current function or program

` From the

Actions

menu, select

Close

If the function or program has unstored changes, you are prompted to check syntax and store before closing.

Running programs and evaluating functions

After defining and storing a function or program, you can use it from an application. All the applications can evaluate functions, but only the

Calculator and Notes applications can run programs.

The program statements are executed in sequential order (although some commands alter the program flow). The output, if any, is displayed in the application’s work area.

• Program execution continues until it reaches the last statement or a

Stop

command.

• Function execution continues until it reaches a

Return

command.

• To stop a program or function manually,

– Windows®: Hold down the

F12

key and press

Enter

repeatedly.

– Macintosh®: Hold down the

key and press

Enter

repeatedly.

– Handheld: Hold down the c

key and press

repeatedly.

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Using short and long names

Anytime you are in the same problem where an object is defined, you can access it by entering its short name (the name given in the object’s

Define

command). This is the case for all defined objects, including private, public, and non-library objects.

You can access a library object from any document by typing the object’s long name. A long name consists of the name of the object’s library document followed by a backslash “\” followed by the name of the object. For example, the long name of the object defined as

func1

in the library document

lib1

lib1\func1

. To type the “\” character on the handheld, press g p

Note: If you cannot remember the exact name or the order of arguments required for a private library object, you can open the library document or use the Program Editor to view the object. You also can use

getVarInfo

to view a list of objects in a library.

Using a Public library function or program

1. Make sure you have defined the object in the document’s first problem, stored the object, saved the library document in the MyLib folder, and refreshed the libraries.

2. Open the TI-Nspire™ application in which you want to use the function or program.

Note: All applications can evaluate functions, but only the Calculator and Notes applications can run programs.

3. Open the Catalog and use the library tab to find and insert the object.

- or -

Type the name of the object. In the case of a function or program, always follow the name with parentheses.

libs2\func1()

4. If the program requires you to supply one or more arguments, type the values or variable names inside the parentheses.

libs2\func1(34,power)

5. Press

Programming 685

Using a Private library function or program

To use a Private library object, you must know its long name. For example, the long name of the object defined as

func1

in the library document

lib1

lib1\func1

Note: If you cannot remember the exact name or the order of arguments required for a private library object, you can open the library document or use the Program Editor to view the object.

1. Make sure you have defined the object in the document’s first problem, stored the object, saved the library document in the MyLib folder, and refreshed the libraries.

2. Open the TI-Nspire™ application in which you want to use the function or program.

Note: All applications can evaluate functions, but only the Calculator and Notes applications can run programs.

3. Type the name of the object. In the case of a function or program, always follow the name with parentheses.

libs2\func1()

4. If the object requires you to supply one or more arguments, type the values or variable names inside the parentheses.

libs2\func1(34,power)

5. Press

Running a non-library program or function

1. Make sure you are in the same problem in which the function or program is defined.

2. Type the name of the function or program on the entry line, or press h

to select the name from a list.

You must always include a set of parentheses after the name.

prog1()

If the function or program requires you to supply one or more arguments, type the values or variable names inside the parentheses.

prog1(34,power)

3. Press

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Interrupting a running program

While a function or program is running, the busy pointer

}

displays.

` To stop the function or program,

– Windows®: Hold down the

F12

key and press

Enter

repeatedly.

– Macintosh®: Hold down the

key and press

Enter

repeatedly.

– Handheld: Hold down the c

key and press

repeatedly.

A message displays. To edit the function or program in the Program

Editor, select

Go To

. The cursor appears at the command where the break occurred.

Getting values into a program

You can choose from several methods to supply the values that a function or program uses in calculations.

Embedding the values within the program or function

This method is useful primarily for values that must be the same each time the program or function is used.

1. Define the program.

2. Run the program.

Letting the user assign the values to variables

A program or function can refer to variables created beforehand. This method requires users to remember the variable names and to assign values to them before using the object.

1. Define the program.

Programming 687

2. Supply the variables, and then run the program.

Letting the user supply the values as arguments

This method lets users pass one or more values as arguments within the expression that calls the program or function.

The following program, , calculates the volume of a cylinder. It requires the user to supply two values: height and radius of the cylinder.

1. Define the program.

(height,radius) =

"Volume =", (

p ¦

radius

height

)

2. Run the program to display the volume of a cylinder with a height of

34 mm and a radius of 5 mm.

(34,5) Volume = 534.071

Note: You do not have to use the parameter names when you run the program, but you must supply two arguments (as values, variables, or expressions). The first must represent the height, and the second must represent the radius.

Requesting the values from the user (programs only)

You can use the and commands in a program to make the program pause and display a dialog box prompting the user for information. This method does not require users to remember variable names or the order in which they are needed.

You cannot use the or command in a function.

1. Define the program.

"Width: ",

"Height: ",

688 Programming

2. Run the program and respond to the requests.

Width: 3 (3 entered as a response)

Height: 23.64 (23.64 entered as a response)

Use instead of when you want the program to interpret the user’s response as a character string rather than a math expression. This avoids requiring the user to enclose the response in quotation marks (““).

Displaying information

A running function or program does not display intermediate calculated results unless you include a command to display them. This is an important difference between performing a calculation on the entry line and performing it in a function or program.

The following calculations, for example, do not display a result in a function or program (although they do from the entry line).

:=12

6 (

/4)

Displaying information in the history

You can use the command in a program or function to display information, including intermediate results, in the history.

12

6 "Result:",(

/4)

Displaying information in a dialog box

You can use the command to pause a running program and display information in a dialog box. The user selects to continue or selects to stop the program.

You cannot use the command in a function.

"Area=" &

Programming 689

Note: Displaying a result with or does not store that result. If you expect to refer later to a result, store it to a global variable.

(

/4)

maximum

Using local variables

A local variable is a temporary variable that exists only while a userdefined function is being evaluated or a user-defined program is running.

Example of a local variable

The following program segment shows a

For...EndFor

loop (which is discussed later in this module). The variable

is the loop counter. In most cases, the variable

is used only while the program is running.

Local i

For i,0,5,1

Disp i

EndFor

Disp i

Declares variable

as local.

Note: When possible, declare as local any variable that is used only within the program and does not need to be available after the program stops.

What causes an undefined variable error message?

Undefined

variable error message displays when you evaluate a userdefined function or run a user-defined program that references a local variable that is not initialized (assigned a value).

For example:

Define fact(n)=Func

Local m

EndWhile

Return m

EndFunc

While n>1 n

m

m: n–1

n

Local variable

is not assigned an initial value.

690 Programming

Initialize local variables

All local variables must be assigned an initial value before they are referenced.

Define fact(n)=Func

Local m: 1

m

While n>1 n

m

m: n–1

n

EndWhile

Return m

EndFunc

1 is stored as the initial value for

Note (CAS): Functions and programs cannot use a local variable to perform symbolic calculations.

CAS: Performing symbolic calculations

If you want a function or program to perform symbolic calculations, you must use a global variable instead of a local. However, you must be certain that the global variable does not already exist outside of the program. The following methods can help.

• Refer to a global variable name, typically with two or more characters, that is not likely to exist outside of the function or program.

• Include

DelVar

within a program to delete the global variable, if it exists, before referring to it. (

DelVar

does not delete locked or linked variables.)

Differences between functions and programs

A function defined in the Program Editor is similar to the functions built into the TI-Nspire™ Software.

• Functions must return a result, which can be graphed or entered in a table. Programs cannot return a result.

• You can use a function (but not a program) within an expression. For example:

func1(3)

is valid, but not

prog1(3)

• You can run programs from Calculator and Notes applications only.

However, you can evaluate functions in Calculator, Notes, Lists &

Spreadsheet, Graphs & Geometry, and Data & Statistics.

Programming 691

• A function can refer to any variable; however, it can store a value to a local variable only. Programs can store to local and global variables.

Note: Arguments used to pass values to a function are treated as local variables automatically. If you want to store to any other variables, you must declare them as

Local

from within the function.

• A function cannot call a program as a subroutine, but it can call another user-defined function.

• You cannot define a program within a function.

• A function cannot define a global function, but it can define a local function.

Calling one program from another

One program can call another program as a subroutine. The subroutine can be external (a separate program) or internal (included in the main program). Subroutines are useful when a program needs to repeat the same group of commands at several different places.

Calling a separate program

To call a separate program, use the same syntax that you use to run the program from the entry line.

Define subtest1()=

Prgm

For i,1,4,1 subtest2(i,i

1000)

EndFor

EndPrgm

Define subtest2(x,y)=

Prgm

Disp x,y

EndPrgm

Defining and calling an internal subroutine

To define an internal subroutine, use the

Define

command with

Prgm...EndPrgm

. Because a subroutine must be defined before it can be called, it is a good practice to define subroutines at the beginning of the main program.

An internal subroutine is called and executed in the same way as a separate program.

692 Programming

Define subtest1()=

Prgm local subtest2

Define subtest2(x,y)=

Prgm

Disp x,y

EndPrgm

©Beginning of main program

For i,1,4,1 subtest2(i,I*1000)

EndFor

EndPrgm

Declares the subroutine as a local variable.

Defines the subroutine.

Calls the subroutine.

Note: Use the Program Editor’s

Var

menu to enter the

Define

and

Prgm...EndPrgm

commands.

Notes about using subroutines

At the end of a subroutine, execution returns to the calling program. To exit a subroutine at any other time, use

Return

with no argument.

A subroutine cannot access local variables declared in the calling program. Likewise, the calling program cannot access local variables declared in a subroutine.

Lbl

commands are local to the programs in which they are located.

Therefore, a

Goto

command in the calling program cannot branch to a label in a subroutine or vice versa.

Avoiding circular-definition errors

When evaluating a user-defined function or running a program, you can specify an argument that includes the same variable that was used to define the function or create the program. However, to avoid circulardefinition errors, you must assign a value for variables that are used in evaluating the function or running the program. For example:

x+1

x

– or –

Programming 693

For i,i,10,1

Disp i

EndFor

Causes a

Circular definition

error message if x or i does not have a value. The error does not occur if x or i has already been assigned a value.

Controlling the flow of a function or program

When you run a program or evaluate a function, the program lines are executed in sequential order. However, some commands alter the program flow. For example:

• Control structures such as

If...EndIf

commands use a conditional test to decide which part of a program to execute.

• Loop commands such as

For...EndFor

repeat a group of commands.

Using If, Lbl, and Goto to control program flow

The

command and several

If...EndIf

structures let you execute a statement or block of statements conditionally, that is, based on the result of a test (such as x>5).

Lbl

(label) and

Goto

commands let you branch, or jump, from one place to another in a function or program.

The

command and several

If...EndIf

structures reside on the Program

Editor’s

Control

menu.

When you insert a structure such as

If...Then...EndIf

, a template is inserted at the cursor location. The cursor is positioned so that you can enter a conditional test.

If command

To execute a single command when a conditional test is true, use the general form:

If x>5

Disp "x is greater than 5"

Disp x

Executed only if x>5; otherwise, skipped.

Always displays the value of x.

In this example, you must store a value to x before executing the

command.

694 Programming

If...Then...EndIf structures

To execute one group of commands if a conditional test is true, use the structure:

If x>5 Then

Disp "x is greater than 5"

2 x

EndIf

Disp x

Executed only if x>5.

Displays the value of:

2x if x>5 x if x

Note:

EndIf

marks the end of the

Then

block that is executed if the condition is true.

If...Then...Else...EndIf structures

To execute one group of commands if a conditional test is true and a different group if the condition is false, use this structure:

If x>5 Then

Disp "x is greater than 5"

5 x

EndIf

Disp x

2 x

Else

Disp "x is less than or equal to 5"

Executed only if x>5.

Executed only if x

{5.

Displays value of:

2x if x>5

5x if x

If...Then...ElseIf... EndIf structures

A more complex form of the

command lets you test for multiple conditions. Suppose you want a program to test a user-supplied argument that signifies one of four options.

Programming 695

To test for each option (If Choice=1, If Choice=2, and so on), use the

If...Then...ElseIf...EndIf

structure.

Lbl and Goto commands

You can also control the flow by using

Lbl

(label) and

Goto

commands.

These commands reside on the Program Editor’s

Transfers

menu.

Use the

Lbl

command to label (assign a name to) a particular location in the function or program.

Lbl

labelName

name to assign to this location (use the same naming convention as a variable name)

You can then use the

Goto

command at any point in the function or program to branch to the location that corresponds to the specified label.

Goto

labelName

specifies which

Lbl

command to branch to

Because a

Goto

command is unconditional (it always branches to the specified label), it is often used with an

command so that you can specify a conditional test. For example:

If x>5

Goto GT5

Disp x

--------

Lbl GT5

Disp "The number was > 5"

If x>5, branches directly to label GT5.

For this example, the program must include commands (such as

Stop

) that prevent

Lbl

GT5 from being executed if x

{5.

Using loops to repeat a group of commands

To repeat the same group of commands successively, use one of the loop structures. Several types of loops are available. Each type gives you a different way to exit the loop, based on a conditional test.

696 Programming

Loop and loop-related commands reside on the Program Editor’s

Control

and

Transfers

menus.

When you insert one of the loop structures, its template is inserted at the cursor location. You can then begin entering the commands that will be executed within the loop.

For...EndFor loops

For...EndFor

loop uses a counter to control the number of times the loop is repeated. The syntax of the

For

command is:

Note: The ending value can be less than the beginning value, provided the increment is negative.

For

variable, begin, end [, increment]

À Á Â Ã

Variable used as a counter

Counter value used the first time

For

is executed

Exits the loop when

variable exceeds this value

Added to the counter each subsequent time

For

is executed (If this optional value is omitted, the

increment is 1.)

When

For

is executed, the

variable value is compared to the end value. If

variable does not exceed end, the loop is executed; otherwise, control jumps to the command following

EndFor

i > 5 i

{

For i,0,5,1

--------

EndFor

--------

Note: The

For

command automatically increments the counter variable so that the function or program can exit the loop after a certain number of repetitions.

At the end of the loop (

EndFor

), control jumps back to the

For

command, where the variable is incremented and compared to

end

For example:

Programming 697

For i,0,5,1

Disp i

EndFor

Disp i

Displays 0, 1, 2, 3, 4, and 5.

Displays 6. When

variable increments to 6, the loop is not executed.

Note: You can declare the counter variable as local if it does not need to be saved after the function or program stops.

While...EndWhile loops

While...EndWhile

loop repeats a block of commands as long as a specified condition is true. The syntax of the

While

command is:

While

condition

When

While

is executed,

condition is evaluated. If condition is true, the loop is executed; otherwise, control jumps to the command following

EndWhile

5 x < 5

While x<5

--------

EndWhile

--------

Note: The

While

command does not automatically change the condition.

You must include commands that allow the function or program to exit the loop.

At the end of the loop (

EndWhile

), control jumps back to the

While

command, where condition is re-evaluated.

To execute the loop the first time, the condition must initially be true.

• Any variables referenced in the condition must be set before the

While

command. (You can build the values into the function or program, or you can prompt the user to enter the values.)

• The loop must contain commands that change the values in the condition, eventually causing it to be false. Otherwise, the condition is always true and the function or program cannot exit the loop

(called an infinite loop).

For example:

698 Programming

0 x

While x<5

Disp x

x+1

x

EndWhile

Disp x

Initially sets x.

Displays 0, 1, 2, 3, and 4.

Increments x.

Displays 5. When x increments to 5, the loop is not executed.

Loop...EndLoop loops

Loop...EndLoop

creates an infinite loop, which is repeated endlessly.

The

Loop

command does not have any arguments.

Loop

--------

EndLoop

--------

Typically, you insert commands in the loop that let the program exit from the loop. Commonly used commands are:

Exit

Goto

, and

Lbl

(label).

For example:

0 x

Loop

Disp x x+1

x

If x>5

Exit

EndLoop

Disp x

command checks the condition.

Exits the loop and jumps to here when

increments to 6.

Note: The

Exit

command exits from the current loop.

Programming 699

In this example, the

command can be anywhere in the loop.

When the If command is:

At the beginning of the loop

At the end of the loop

The loop is:

Executed only if the condition is true.

Executed at least once and repeated only if the condition is true.

The

command could also use a

Goto

command to transfer program control to a specified

Lbl

(label) command.

Repeating a loop immediately

The

Cycle

command immediately transfers program control to the next iteration of a loop (before the current iteration is complete). This command works with

For...EndFor

While...EndWhile

, and

Loop...EndLoop

Lbl and Goto loops

Although the

Lbl

(label) and

Goto

commands are not strictly loop commands, they can be used to create an infinite loop. For example:

Lbl START

--------

Goto START

--------

As with

Loop...EndLoop

, the loop should contain commands that let the function or program exit from the loop.

Changing mode settings

Functions and programs can use the

setMode()

function to temporarily set specific calculation or result modes. The Program Editor’s

Mode

menu makes it easy to enter the correct syntax without requiring you to memorize numeric codes.

Note: Mode changes made within a function or program definition do not persist outside the function or program.

Setting a mode

1. Position the cursor where you want to insert the

setMode

function.

2. From the

Mode

menu, select the mode to change, and select the new setting.

The correct syntax is inserted at the cursor location. For example:

700 Programming

Debugging programs and handling errors

After you write a function or program, you can use several techniques to find and correct errors. You can also build an error-handling command into the function or program itself.

If your function or program allows the user to select from several options, be sure to run it and test each option.