**HP Prime Custom App: GeomCalc**

**Introduction**

The app GeomCalc is an example of a custom HP App for the HP
Prime. For general information, please
visit this blog entry: http://edspi31415.blogspot.com/2018/02/hp-prime-intro-to-blank-custom-apps.html

Let’s get start with this example app.

**START - The Initial Conditions**

Here I set the app’s angle to degrees mode. Note that I use the variable AAngle instead
of the global variable HAngle. The
values for AAngle are slightly different than HAngle:

0: use the angle
setting from Home Settings

1: Radians

2: Degrees

3: Gradians

I want the app to operate with angles in degrees, so I set
AAngle to 1.

The last command is a message box containing the word Ready,
to let the user know that the app is all set to go.

START()

BEGIN

// Set app angle to degrees

AAngle:=2;

MSGBOX("Ready.");

END;

**Info – Title and Introduction**

I want to leave some basic information about this app. I recommend that you use the PRINT command
rather than the TEXTOUT/WAIT/FREEZE.
Alternatively, you can store a string in ANote.

I prefer using PRINT because I can print multiple lines with
appropriate line breaks.

Info()

BEGIN

PRINT();

PRINT("GeomCalc");

PRINT("---------");

PRINT("EWS 2018-02-07");

PRINT("---------");

PRINT("Geometry areas and
volumes");

END;

**The Symb section – selecting the calculation**

In this section, I set the variable

*I*to a choice of one of ten options. The variable*I*is a global variable, so I can use determine calculations. The INPUT command uses a dropdown box. The general format for a single dropdown box is:
INPUT( { { var, {“choice 1”,
“choice 2”, … }}},

*… (other parameters)*)
The message box at the end let’s the user know that the
choice has been set, and can now proceed to the calculation by pressing
[Num].

Symb()

BEGIN

// Choose the calculation

// Global vars are used

INPUT({{I,{"Area: Circle",

"Area: Ellipse",

"Area: Trapezoid",

"Area: Circular Sector",

"Area: Regular Polygon",

"Volume: Sphere",

"Volume: Cylinder",

"Volume: Cone",

"Volume: Box",

"Volume: Ellipsoid"}}},

"Select Your
Calculation");

MSGBOX("It's set!");

END;

**The Num section – doing the calculation**

When the [Num] is pressed, the user as asked to enter the
arguments. The final result is displayed
on the terminal. Since global variables
(including A-Z) is used, values are permanently stored until changed. In this app, I store the area in the variable

*E*and the volume in*V*.
There is no default selection, so I use ten IF-THEN
structures than a CASE structure.

Num()

BEGIN

IF I==1 THEN

INPUT(R,"Area:
Circle","Radius: ");

E:=π*R^2;

PRINT();

PRINT("Area: "+E);

END;

IF I==2 THEN

INPUT({A,B},"Area:
Ellipse",

{"A: ","B: "});

E:=π*A*B;

PRINT();

PRINT("Area: "+E);

END;

IF I==3 THEN

INPUT({A,B,H},"Area: Trapezoid",

{"A: ","B:
","H: "});

E:=0.5*H*(A+B);

PRINT();

PRINT("Area: "+E);

END;

IF I==4 THEN

INPUT({θ,R},"Area: Circular

Sector",{"Angle (°):
",

"Radius: "});

E:=θ*π*R^2/360;

PRINT();

PRINT("Area: "+E);

END;

IF I==5 THEN

INPUT({N,S},"Area: Regular

Polygon",{"# sides:
",

"Length: "});

E:=N*S^2/(4*TAN(180/N));

PRINT();

PRINT("Area: "+E);

END;

IF I==6 THEN

INPUT(R,"Volume:
Sphere","Radius: ");

V:=4/3*π*R^3;

PRINT();

PRINT("Volume: "+V);

END;

IF I==7 THEN

INPUT({R,H},"Volume:
Cylinder",

{"Radius: ","Height:
"});

V:=π*R^2*H;

PRINT();

PRINT("Volume: "+V);

END;

IF I==8 THEN

INPUT({R,H},"Volume:
Cone",

{"Radius: ","Height:
"});

V:=π*R^2*H/3;

PRINT();

PRINT("Volume: "+V);

END;

IF I==9 THEN

INPUT({A,B,C},"Volume:
Box",

{"A: ","B:
","C: "});

V:=A*B*C;

PRINT();

PRINT("Volume: "+V);

END;

IF I==10 THEN

INPUT({A,B,C},"Volume:
Ellipsoid",

{"A: ","B:
","C: "});

V:=4/3*π*A*B*C;

PRINT();

PRINT("Volume: "+V);

END;

END;

**Putting It All Together**

#pragma mode( separator(.,;)
integer(h32) )

Symb()

BEGIN

// Choose the calculation

// Global vars are used

INPUT({{I,{"Area: Circle",

"Area: Ellipse",

"Area: Trapezoid",

"Area: Circular Sector",

"Area: Regular Polygon",

"Volume: Sphere",

"Volume: Cylinder",

"Volume: Cone",

"Volume: Box",

"Volume: Ellipsoid"}}},

"Select Your
Calculation");

MSGBOX("It's set!");

END;

//Plot()

//BEGIN

// MSGBOX("Plot");

//END;

Num()

BEGIN

IF I==1 THEN

INPUT(R,"Area:
Circle","Radius: ");

E:=π*R^2;

PRINT();

PRINT("Area: "+E);

END;

IF I==2 THEN

INPUT({A,B},"Area:
Ellipse",

{"A: ","B: "});

E:=π*A*B;

PRINT();

PRINT("Area: "+E);

END;

IF I==3 THEN

INPUT({A,B,H},"Area: Trapezoid",

{"A: ","B:
","H: "});

E:=0.5*H*(A+B);

PRINT();

PRINT("Area: "+E);

END;

IF I==4 THEN

INPUT({θ,R},"Area: Circular

Sector",{"Angle (°):
",

"Radius: "});

E:=θ*π*R^2/360;

PRINT();

PRINT("Area: "+E);

END;

IF I==5 THEN

INPUT({N,S},"Area: Regular

Polygon",{"# sides:
",

"Length: "});

E:=N*S^2/(4*TAN(180/N));

PRINT();

PRINT("Area: "+E);

END;

IF I==6 THEN

INPUT(R,"Volume:
Sphere","Radius: ");

V:=4/3*π*R^3;

PRINT();

PRINT("Volume: "+V);

END;

IF I==7 THEN

INPUT({R,H},"Volume:
Cylinder",

{"Radius: ","Height:
"});

V:=π*R^2*H;

PRINT();

PRINT("Volume: "+V);

END;

IF I==8 THEN

INPUT({R,H},"Volume:
Cone",

{"Radius: ","Height:
"});

V:=π*R^2*H/3;

PRINT();

PRINT("Volume: "+V);

END;

IF I==9 THEN

INPUT({A,B,C},"Volume:
Box",

{"A: ","B:
","C: "});

V:=A*B*C;

PRINT();

PRINT("Volume: "+V);

END;

IF I==10 THEN

INPUT({A,B,C},"Volume:
Ellipsoid",

{"A: ","B:
","C: "});

V:=4/3*π*A*B*C;

PRINT();

PRINT("Volume: "+V);

END;

END;

//SymbSetup()

//BEGIN

// MSGBOX("SymbSetup");

//END;

//PlotSetup()

//BEGIN

// MSGBOX("PlotSetup");

//END;

//NumSetup()

//BEGIN

// MSGBOX("NumSetup");

//END;

Info()

BEGIN

PRINT();

PRINT("GeomCalc");

PRINT("---------");

PRINT("EWS 2018-02-07");

PRINT("---------");

PRINT("Geometry areas and
volumes");

END;

START()

BEGIN

// Set app angle to degrees

AAngle:=2;

MSGBOX("Ready.");

END;

//RESET()

//BEGIN

// MSGBOX("RESET");

//END;

//VIEW "Views", Views()

//BEGIN

// MSGBOX("Views");

//END;

**Examples**

Example 1: Area of a Polygon

Example 2: Volume of a Cone

I plan to post another example by next week, that one will involve plotting.

Eddie

This blog is property of Edward
Shore, 2018

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