1 / 20

Introducing ASML

Introducing ASML. Methods, Values, Constraints, Constants, Variables Lecture 10 Software Engineering COMP201. I. Methods. Methods are named operations that may be invoked in various contexts

saxton
Download Presentation

Introducing ASML

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introducing ASML Methods, Values, Constraints, Constants, Variables Lecture 10 Software Engineering COMP201

  2. I. Methods • Methods are named operations that may be invoked in various contexts • The definition of a method may include parameters that will be associated with particular values each time the method is invoked • Methods may also specify a return value that is available after the operation has been performed

  3. The general form for a method definition The type of the return value, if there is one name (parameter 1 as Type, … parameter n as Type)as Type the name of method the values sent to the method, if there any

  4. Method IsWord() • An expression in the form IsWord() is an application of the name IsWord to argument i, which is a long integer. • IsWord evaluates an argument i and returns the value true if i 0 and i0xFFFF (hexadecimal number). • If i doesn’t fit these criteria, IsWord returns the value false. IsWord ( i as Integer ) as Boolean return (0<= i and i <= 0xFFFF) Main() step if IsWord ( 123 ) then Writelone (“123 is a word of memory.”)

  5. Functions and update procedures • Functions have no effect on state variables • Functions must return a value IsWord ( i as Integer ) as Boolean return (0<= i and i <= 0xFFFF) • Update procedures configure the values of state variables for the next sequential step of the machine • Update procedures may optionally return a value

  6. Update procedure power() var x as Integer = 3 var y as Integer = 0 var index as Integer = 3 power (x as Integer, n as Integer) as Integer var result as Integer = 1 var i as Integer = 1 step while i<=n result:=result*x i:=i+1 step return result Main() step y := power(5,3) step WriteLine (“5 cubed =” +y) WriteLine(“3 cubed =” + power(3,index)) x:= power(x, power(2,2)) step WriteLine (“x = ” +x) Output: 5 cubed = 125 3 cubed = 27 x = 81

  7. Main() mySet = {1, 2, 3} step WriteLine(“mySet has” + asString(size(mySet))+ “ elements. ”) Local names for values Statement in the form identifier = expression introduce identifier as a local name for the value given on the right hand side of the equals sign (“ = ”) by expression. Local names may be introduced within any block of statement. Local names could appear after the “then” keyword of an if … then … else statement

  8. Local names in sequences of steps • A local name can be referenced anywhere in its statement block. • In a sequence of steps, local namesintroduced within a step block are available within any following step block. Main() step mySet1 = {1, 2, 3} WriteLine (“mySet has” + asString(size(mySet1))+ “ elements. ”) step mySet2 = mySet1 union {4 , 5, 6} WriteLine(“mySet has” + asString(size(mySet2))+ “ elements. ”)

  9. Method overloading Method overloading allows you: • to use the same name in different methods • in each instance to have the compiler choose the correct instance Must be a clear way for the compiler to decide which method should be called for any particular instance The KEY for this is the parameter list

  10. Method overloading example S = { 1, 8, 2, 12, 13, 6} Max(i as Integer, j as Integer)as Integer returnif i > j then i else j Max(s as Set of Integer)as Integer returnany m | m in S where not (exists n in S where n>m ) run() stepwriteln(“The largest number in the set is ” + ( Max(S) ) ) stepwriteln(“The largest of the two integers is ” + ( Max(2,3) ) ) A series of methods with the same name but differentiated by their parameter lists are overloaded methods

  11. II.ValuesWhat are values? The term value has the same meaning as in mathematical sets Value A value is an immutable element that supports two operations: equality testing and set membership. If x and y are values, then we can ask whether x is equal to y If the S is a set, then we can ask whether x is an element of S x in S x = y

  12. ordered pair value ( x , y ) Structured values • Some values are composed of other values • Some structured values are built into AsmL; others may be defined by you structure Location base as Integer offset as Integer Location (1,4) is a value of the user-defined structure type Location

  13. Data Type Meaning Boolean A type that can be assigned true and false Byte 8-bit unsigned integer type Short 16-bit signed integer type Integer 32-bit signed integer type Long 64-bit signed integer type Float Single-precision 32-bit floating-point format type as specified in IEEE 754 Double Double-precision 64-bit floating-point format type as specified in IEEE 754 Built in value types

  14. Built in value types Data Type Meaning Char Unicode character type String Unicode string type Seq of A A sequence of elements of type A Set of A A set containing elements of type A Map of A to B A table whose entries map of elements of type A to type B

  15. Built in value types Data Type Meaning (A1,A2,…) A tuple consisting of elements of type A1, A2, … Tuple values are written in the same form For example, (1,2) is of a value of the built-in type (Integer,Integer) A? Types in the form t? includes all of the values of type t plus the special value undef. For example, a variable declared as Boolean? could contain either of the Boolean value true or false or the value undef.

  16. III. Constraints Assertions • Assertionsrequire and ensure statements document constraints placed upon the model • Violating a constraint at runtime is called an assertion failure AllTickets = {1..1024} IsTicketID (i as Integer) as Boolean require i > 0 return ( i in AllTickets) ChooseAnyTicket() as Integer ensure IsTicketID(result) return any t | t in AllTickets • The keyword result denotes the value of the return statement

  17. Type constraints • Types of constants, variables and method parameters may be specified using the syntax : nameastype • Types may be explicitly checked using the “ is” operator : valueistype an expression will be either true or false, depending on whether the value given is an element of the type • Types are not themselves values. For example, you can’t pass a type as an argument

  18. IV. Constants • Constants are fixed, named values • Constants can either be global or local • Global constants are declared in the beginning of the program • Local constants are declared within a statement block • The general form of declaring and initialising a constant is: Name [as Type] = value MaxInteger = 100 run() MinInteger = 0

  19. V. Variables • Variables are names given to memory locations. • Updating variables is the only way to change a state of a machine. • Variables can be complex types such as structures or maps as well as simple types. • Here is the general form for declaring and initialising variables: varname[asType] = value

  20. Types of variables • There are three types of variables in AsmL • Global variables • Local variables • Instance-based variables Instance-based variables are variables that exist for each instance of a class var x as Integer = 10 // shows explicit typing var x = 10 // shows implicit typing var greeting as String = “Hello” // shows a // string variable var y = [1..6] // shows a sequence of // integers from 1 to 6 var menu = {“ham”, “cheese”, “bit”} // shows a // set

More Related