Programming on the Go
Chapters 1and 2
Siddharth Patel
1000773753
Administrator
INTRODUCTION
INSTALLING TOUCHDEVELOP
SCRIPTING LANGUAGE
IMPORTANT WEBSITES
What Is Touchdevelop-definition
TouchDevelop is an application development environment which allows
users to script and design applications their mobile devices.
•
•
The apps developed using Touchdevelop can use sensors, media,
data on mobile, tablets or PC
The scripts can interacts with cloud services including storage
computing and social networks.
What Can Be Done Using Touchdevelop?
Games ,productive apps, personalized phone …
Why?-Smartphones VS PCs
• In future smartphone might me the only computing device.
SMARTPHONE
CAPABILITIES
Yes
TEXT
Yes
TALK
Yes
EMAIL
Yes
GAMES
Yes
NAVIGATION
No
PROGRAMMING
Traditional Mobile App Development Technique
• Use Computer to make
mobile App
• Download APIs, SDK or need
specific software
• For testing on mobile connect
phone to computers
• Share project with
teammates using hosting
server
Touchdevelop Benefits and Challenges
Benefits
•
No specific device need
•
No need to install huge
SDKs for do specific
settings.
• Share project or scripts
with teammates on
touchdevelop itself
Challenges
• Mobile Phone Small
Screen
• No Keyboard
• Touch screen
interface as input
Installing Touchdevelop on a Windows Phone
1. Tap the Marketplace tile on the Windows phone.
2. Press the search icon at the bottom of the screen, and type
the text ‘touchdevelop’ into the Marketplace Search text
box. Before you finish typing all the letters, the
TouchDevelop app should appear as a choice on the screen.
3. Tap that choice to select it.
4. Tap Install.
Installing Touchdevelop on Other Platforms
Touchdevelop runs on web browser on any device
Supported Browsers
• IE 10
• Chrome(mobile)
• Firefox
• Safari(mobile)
1. Go to https://www.touchdevelop.com/app/#
2. Log in and that’s it!
The TouchDevelop Ecosystem
the script can be shared on cloud
infrastructure
A user can share, comment, like the
scripts
User can find scripts in different
categories like new, top featured,
installed.
The Web interface
It’s the same as the phone interface
Mouse
Keyboard
Larger screen
helps to increase productive to user might prefer the web interface but
the PC may not have all the sensors like phone (GPS).
Demo
The Scripting Language
• Statement oriented.
• Statements are executed in a sequential manner.
• The language is strongly typed.
• Its not an object oriented language.
Data types
The Nothing Type
• A method or an operation which does not return a usable result, but which otherwise succeeded,
actually returns a value of type Nothing.
• The sole value of type Nothing does not require any storage. Therefore this type is neither a value
type nor a reference type. It is a special case.
The Invalid Type
• The Invalid Value: every data type has special value as Invalid value, it is assigned to show that the global
variable has not been initialized or the method was unable to return the value.
Example
var numUsers := 0
…
if connection failure detected then
numUsers := invalid → number
else
…
if numUsers → is invalid then
“Script is terminating” → post to wall
else
Data types contd.
Value Type
Value types storages on the stack used for local variables. The storage is automatically
deallocated on exit from an action.(Actions is called functions in other langualges ).
Number:
• combines the integer and floating-point
• IEEE 754 (plus infinity, minus infinity can be computed)
String :
• A sequence of zero or more Unicode characters.
• Showed as doublequote and backslash are used for special characters.
Boolean:
• The type whose constants are true and false.
Data types contd.
Value Type
Data types contd.
Reference Type
• Global defined variables are stored as Reference Type.
• Storage for an instance of a reference type is allocated in a
different place from a variable declared with that type. A local
variable with a reference type is implemented as a pointer (a
reference) to the actual value which is stored elsewhere.
• If the value represents any entity which exists outside
TouchDevelop, then storage is allocated outside the TouchDevelop
application.
• Otherwise the storage is allocated within an area of memory
controlled by TouchDevelop which is called the heap.
Data types contd.
Reference Type
Data types contd.
Reference Type
Data types contd.
Reference Type
Data types contd.
Collection Types
• Touchdevelop provides homogeneous collections.
• A collection contains zero or more elements whose type is one of the value types or
one of the reference types
• Collections which allow to insert or delete an element is called mutable, others are
immutable .
Art Items
Some scripts need to display pictures or to produce sounds. These pictures or
sounds can be added to the script as global constants and become part of the
script. Such items are held in the Art section of the script.
Expressions
Explicit Constants
Number constants are regular IEEE 754 standard 64 bit floating point numbers.
String constants can be entered using Touchdevelop editor and string is
implemented as Sequence of Unicode characters.
Named Constants
Touchdevelop has mechanism to construct constants for color and sounds.
Such constants are called name constants.
Demo
Variables
Local Variables
Local variables follow the usual visibility rules and lifetime rules for block structured
languages.
var s1 := “Hello!”
Global Data Variables
The data section of a script contains declarations for variables which are accessible by
all actions within the script.
If the type is Number, Boolean, String or DateTime, the variable has a neutral initial
value. It is 0, false, “” or 1 January 0001 12:00 am respectively. For any other datatype,
the initial value is invalid.
An access to a global data variable inside a script uses the special symbol ◳ .
◳game := media → create board(480)
Operators
Operators Contd..
Statements
Expression: Any expression may be used as a statement. For example, this is a valid statement.
(“Hello “ || “ there!”) → post to wall
Declaration and Assignment: A declaration of a local variable is combined with an assignment to
initialize the variable.
var places := collections → create location collection
If an action has more than one return parameter.
var street name := “”
var street number := 0
street name, street number := ▷Get Address Info(“Joanie”)
If Statement: The TouchDevelop editor always generates the if-then-else form for an if
statement, supplying empty bodies for the then clause and the else clause.
if a < b then
if a < c then
min := a
else min := c
else if b < c then
min := b
else
min := c
Statements Contd..
While Loop: while loop has a controlling expression which must evaluate to a Boolean
value. The loop body is repeatedly executed as long as the controlling expression evaluates to true.
var long song := invalid → song
var my music := media → songs
var num songs := my music → count
var i := 0
while i < num songs and long song → is invalid do
var sng := my music → at(i)
if sng→ duration > 10*60 then
long song := sng
else
// nothing
i := i + 1
For Loop: The for loop in TouchDevelop is similar to for loops in other programming Languages, but
with some added constraints. The index variable must be a Number; it must be initialized to zero
for the first iteration and it must be incremented in steps of one.
For Each Loop: A for each loop is used for iterating through all the elements of a collection.
Actions
Actions are basically the function of other languages.
An action can have zero or more input parameters and zero or more result parameters.
For example, consider the action Replicate defined as follows.
action Replicate( s: String, n: Number ) returns r: String
r := “”
while n > 0 do
r := r || s
n := n – 1
The action can be invoked and its resulting value used in a statement like the
following.
(“The answer is “ || ▷Replicate(“NO! “, 10) || “forever!”)→ post to wall
When an action is invoked, each result parameter is initialized to an invalid value of the
correct type. When control reaches the end of the action, the final values of the result
parameters are returned as the results of the call.
Calling a Library Action
An action can be invoke action in a script which has been declare as library.
Each such library script must be added to the library section of the script.
When editing code in the script, the editor provides a button labeled ♻libs.
Tapping this key inserts the symbol ♻ into the code and the editor then
provides a choice between the various names used for the imported library
scripts. Once a name has been selected, the editor allows any action in that
library script, other than those marked as private, to be called.
There is no direct access to any global data items or art items declared in
the script.
Creating Library Scripts
While editing the property of a script tick to the check box option library converts the script in to library.
A library script cannot define any entries in its Events or Records sections.
Events
Events are like actions. They cannot be invoked they must invoke when some external action happens.
It might be phone sensors, like shaking the phone or touch to a particular area.
An event will interrupt the normal execution of a script.
However an event will never interrupt the code for another event while it is still executing.
IMPORTANT WEBSITES
•
•
•
•
https://www.touchdevelop.com/app/#
http://research.microsoft.com/en-us/projects/touchdevelop/
https://www.touchdevelop.com/slides
https://www.touchdevelop.com/learn
REFERENCES
1. https://www.touchdevelop.com/book
2. introduction to touchdevelop presentation at https://www.touchdevelop.com/slides