Programmer’s Guide to F

Structures and Derived Datatypes

Structures and Derived Datatypes

Arrays allow data to be grouped, but only if all items have the same data type.

It is often useful to use a structure, which is a compound object consisting of values that may be of different data types.

Structures and Derived Datatypes

Derived types are used to define the form of the structures.

6.1 Structures

A structure is a collection of values, not necessarily of the same type.

The objects that make up a structure are called its components.

6.1 Structures

A good example of the use of a structure might be provided by a simple list, consisting of line numbers and statements on each line.

1 statement12 statement23 statement3: :: :

6.1 Structures

This list can be represented as 2 arrays, one to hold line numbers and one to hold the text of each line.

6.1 Structures

Perhaps, a better way to do this is to have a single object called line consisting of two components, an integer line_number and a character string statement.The entire list would then be an array of these structures, one for each line.

6.1 Structures

A slightly more complicated example: Suppose we wish to store in our

computer the contents of our little black book that contains names, addresses, phone numbers, and some remarks about each person.

6.1 Structures

The name of the structure is person.It has 4 components: name, address, phone, and remarks.

person

name

address

phone

remarks

6.1 Structures

Sometimes the components might be broken down into lower-level components.For instance, the address itself could be a structure with components number, street, city, state, and postal zip_code.

6.2 Derived Types

As we discussed before, there are 5 intrinsic F data types: integer real complex logical character

6.2 Derived Types

A programmer may define a new data type, called a derived type.

6.2 Derived Types

A type definition begins with the keyword type, followed by either private or public accessibility attribute, followed by two colons (::) and the name of the type being defined.

6.2 Derived Types

The components of the type are given in the ordinary type declarations.The type definition ends with the keywords end type, followed by the name of the type being defined.

All type definitions must be put in a module.

6.2 Derived Types

Let’s start with our first example, a list containing line numbers and statements.type, public :: line

integer :: line_numbercharacter (len = line_length) :: text

end type line where line_length is an integer parameter

(named constant)

6.2 Derived Types

Let’s return to the example of the little black book.To define the type phone_type in that example, area_code and number are each declared to be integer components.

phone_type

area_code

number

6.2 Derived Types

type, public :: phone_typeinteger :: area_code,

numberend type phone_type

phone

area_code

number

6.2 Derived Types

The definition od the type address_type is a little more complicated because some of the components are character strings and some are integers.

6.2 Derived Types

type, public :: address_typeinteger :: numbercharacter (len=30) :: street, citycharacter (len=2) :: stateinteger :: zip_code

end type address_type

address

number

street

city

state

zip_code

6.2 Derived Types

Now that, the types address_type and phone_type are defined, it is possible to define a type suitable for one entry in the black book.Note that the names address_type and phone_type were used for the names of the types, so that the names address and phone could be used for the components of the type person_type.

6.2 Derived Types

type, public :: person_typecharacter (len=40) :: nametype (address_type) :: addresstype (phone_type) :: phonecharacter (len=100) :: remarks

end type person_type

6.2 Derived Types

type, public :: person character(len=12) :: first_name character(len=1) :: middle_initial character(len=12) :: last_name integer :: age

character(len=1) :: sex ! M or Fcharacter(len=5) :: tax_number

end type person

6.3 Declaring and Using Structures

Given the type definition for line that can be used to hold a line number and one statement, a variable new_line that could be used to represent one line of the list that can be declared bytype (line) :: new_line

6.3 Declaring and Using Structures

The entire list could be represented by a single variable declared to be an array of values of type line:

type (line), dimension (max_lines) :: list

6.3 Declaring and Using Structures

For example, to print a line of the list: If two arrays were usedprint “(i5, tr1, a)”, line_number(n),

text(n)

With this declarationprint “(i5, tr1, a)”, list(n)

6.3 Declaring and Using Structures

To use the type declarations for the address book, joan can be declared to be type person_type with the statementtype (person_type) : joan

and the little black book can be declared to be an array of type person_type:

type (person_type), dimension (1000) :: black_book

6.3 Declaring and Using Structures

Any program or module that is to contain a derived type declaration must use the module containing the derived type definition (or be in the module).

6.3.1 Referencing Structure Components

A component of a structure is referenced by writing the name of the structure by a percent sign (%) and then the name of the component

6.3.1 Referencing Structure Components

Suppose joan is an f variable declared to be type person_type. Then Joan’s address is referenced by the expressionjoan % address

The object joan%address is itself a structure. If it is desired to refer to one of the components of this structure, another percent symbol is used.joan % address % state

andjoan % phone % area_code

6.3.2 Structure Constructors

Each derived-type declaration creates a structure constructor, whose name is the same as that of the derived type. For example, if you define a type

named boa, you have a boa constructor.

6.3.2 Structure Constructors

The arguments are values to be placed in the individual components of the structure. For example, using the type

phone_type, an area code and telephone number may be assigned with the statement

joan % phone = phone_type (505, 2750800)

6.3.2 Structure Constructors

It is not necessary that the function arguments be constants. If joan%address has been given a value, the variable joan of type person_type can be assigned a value with the statementjoan = person_type (“Joan Doe”, john

%address, &phone_type (505, fax_number – 1), &“Same address as husband John”)

type, public :: employee type(person) :: employee character(len=20) department real :: salaryend type employee

type(person) :: saadetsaadet%employee%age = 34

Now you can declare variable of type person:

type ( type _name ) : : list_of_identifiers

type(person) :: ali, mukaddes, veli

Putting data in a derived type variable

ali = person("Ali","M","Aktepe",56,"M","45645")

mukaddes =person("Mukaddes"," ","Has",18,"F","12345")

veli = person("Veli","M","Karatepe",65,"M","34567")

This is a structure constructor

module kompleks type, public :: kom real :: gercek, sanal end type komend module kompleksprogram ornek use kompleks type(kom) :: s1, s2, top, fark, carpim print *, "Birinci kompleks sayiyi yaziniz." read *, s1 print *, "ikinci kompleks sayiyi yaziniz." read *, s2 !iki kompleks sayinin toplami. top%gercek=s1%gercek + s2%gercek top%sanal =s1%sanal + s2%sanal fark%gercek=s1%gercek- s2%gercek fark%sanal =s1%sanal - s2%sanal carpim%gercek= s1%gercek*s2%gercek - s1%sanal*s2%sanal carpim%sanal = s1%gercek*s2%sanal + s1%sanal*s2%gercek print *,"s1+s2=", top print *,"s1-s2=", fark print *,"s1*s2=", carpimend program ornek

program e_8_3 use m1 type(nokta) :: m,p real :: yaricap, a,b,c,d,e print *, "Cemberin merkezinin koordinatlarini ",& "girin (x,y)." read *, m print *, "Cember uzerindeki bir noktanin ", & "koordinatlarini girin (x,y)." read *, p print *, " " print *, "Cemberin yaricapi", rds(p,m),"dir." print *, " " a = 1.0 b = 1.0 c = -2.0*m%x d = -2*m%y e = (m%x)**2 + (m%y)**2 - (rds(p,m))**2 print *, "Cember denkleminin," print *, "ax2+by2+cx+dy+e=0 formundaki katsayilari:" print *, "a=",a print *, "b=",b print *, "c=",c print *, "d=",d print *, "e=",eend program e_8_3

module m1

public :: rds

type, public :: nokta

real :: x, y

end type nokta

contains

function rds(p,m) result(r)

type(nokta), intent(in) :: p, m

real :: r

real :: g1, g2 ! Ara islemlerde kullanilan

! yerel/gecici degiskenler.

g1 = (p%x - m%x)**2

g2 = (p%y - m%y)**2

r = sqrt(g1 + g2)

end function rds

end module m1

program e_8_4

use m1

type(aile), dimension(4) :: diaz

integer :: i

do i=1,4

print *, "Ad, soyad, cinsiyet(E,K), yas, meslek",&

" bilgilerini giriniz."

print *, "Adres bilgilerinizi girin.(genel, semt, il, ulke)"

read *, diaz(i)

print *, "Adiniz ",trim(adjustl(diaz(i)%kssl%ad))//" "// &

trim(adjustl(diaz(i)%kssl%sad))//"."

print *, diaz(i)%kssl%yas,"yasindasiniz cinsiyetniz ",diaz(i)%kssl%cins, &

" ve mesleginiz ",diaz(i)%kssl%meslek,"."

end do

print *, "Adresiniz:"

print *, trim(adjustl(diaz(i)%addr%genel))

print *, diaz(i)%addr%semt

print *, diaz(i)%addr%il

print *, diaz(i)%addr%ulke

end program e_8_4

module m1

type, public ::kibil

character (len=20) :: ad, sad

character (len=1) :: cins ! E,K

integer :: yas

character (len=20) :: meslek

end type kibil

type, public :: adres

character (len=100):: genel

character (len=20) :: semt, il, ulke

end type adres

type, public :: aile

type(kibil) :: kssl

type(adres) :: addr

end type aile

end module m1