C Library Functions - M_list (3)
NAME
M_list(3f) - [M_list::INTRO] maintain simple lists (LICENSE:PD)
CONTENTS
Synopsis
Description
Examples
Examples
Author
License
SYNOPSIS
use M_list, only : insert, replace, remove, locate use M_list, only : dictionary
DESCRIPTION
The M_list(3fm) module allows for maintaining an allocatable array of intrinsic type (REAL, INTEGER, CHARACTER) as a sorted list. An example is given that creates a keyword-value dictionary using the lists.
The lists are maintained as simple allocatable arrays. Each time an entry is added or deleted the array is re-allocated. Because of the expense of reallocating the data these routines are best suited for maintaining small lists that do not change size frequently.
The advantage of this simplistic approach is that the dictionary components are simple arrays of intrinsic types which can be easily accessed with standard routines. It is easy to understand, as it works with simple arrays. For more demanding applications this would be implemented as a linked list, which there are a number of freely available examples of; several are listed on the Fortran Wiki.
BASIC LIST
subroutine locate(list,value,place,ier,errmsg) finds the index where a value is found or should be in a sorted array and flag if the value exists already subroutine insert(list,value,place) insert entry into an allocatable array at specified position subroutine replace(list,value,place) replace entry in an allocatable array at specified position subroutine remove(list,place) remove entry from an allocatable array at specified position
EXAMPLES
Sample program
program demo_M_list use M_list, only : insert, locate, replace, remove ! create a dictionary with character keywords, values, and value lengths ! using the routines for maintaining a listResultsuse M_list, only : locate, insert, replace implicit none character(len=:),allocatable :: keywords(:) character(len=:),allocatable :: values(:) integer,allocatable :: counts(:) integer :: i ! insert and replace entries call update(’b’,’value of b’) call update(’a’,’value of a’) call update(’c’,’value of c’) call update(’c’,’value of c again’) call update(’d’,’value of d’) call update(’a’,’value of a again’) ! show array write(*,’(*(a,"==>","[",a,"]",/))’)& & (trim(keywords(i)),values(i)(:counts(i)),i=1,size(keywords)) ! remove some entries call update(’a’) call update(’c’) write(*,’(*(a,"==>","[",a,"]",/))’)& & (trim(keywords(i)),values(i)(:counts(i)),i=1,size(keywords)) ! get some values write(*,*)’get b=>’,get(’b’) write(*,*)’get d=>’,get(’d’) write(*,*)’get notthere=>’,get(’notthere’) ! contains subroutine update(key,valin) character(len=*),intent(in) :: key character(len=*),intent(in),optional :: valin integer :: place integer :: ilen character(len=:),allocatable :: val if(present(valin))then val=valin ilen=len_trim(val) ! find where string is or should be call locate(keywords,key,place) ! if string was not found insert it if(place.lt.1)then call insert(keywords,key,iabs(place)) call insert(values,val,iabs(place)) call insert(counts,ilen,iabs(place)) else call replace(values,val,place) call replace(counts,ilen,place) endif else call locate(keywords,key,place) if(place.gt.0)then call remove(keywords,place) call remove(values,place) call remove(counts,place) endif endif end subroutine update function get(key) result(valout) character(len=*),intent(in) :: key character(len=:),allocatable :: valout integer :: place ! find where string is or should be call locate(keywords,key,place) if(place.lt.1)then valout=’’ else valout=values(place)(:counts(place)) endif end function get end program demo_M_list
> d==>[value of d] > c==>[value of c again] > b==>[value of b] > a==>[value of a again] > > d==>[value of d] > b==>[value of b] > > get b=>value of b > get d=>value of d > get notthere=>
BASIC DICTIONARY
A basic dictionary that uses the basic M_list functions.
Consider using generic linked-list based dictionaries when heavy usage is required, now that that is available in more recent versions of Fortran.
Note: this does not work with gfortran(1) up to at least 7.4.0 but works from at least 10.3.0 and onward.
Dictionary type definition:
type dictionary character(len=:),allocatable :: key(:) character(len=:),allocatable :: value(:) integer,allocatable :: count(:) contains procedure,public :: get => dict_get procedure,public :: set => dict_add procedure,public :: del => dict_delete procedure,public :: clr => dict_clear end type dictionary%get get value from type(dictionary) given an existing key %set set or replace value for type(dictionary) given a key %del delete an existing key from type(dictionary) %clr empty a type(dictionary) %ifdef test if name is defined
EXAMPLES
Sample program
program test_dictionary use M_list, only : dictionary implicit none type(dictionary) :: table ! ! create a character string dictionary ! call table%set(’A’,’aye’) call table%set(’B’,’bee’) call table%set(’C’,’see’) call table%set(’D’,’dee’) ! write(*,*)’A=’,table%get(’A’) write(*,*)’C=’,table%get(’C’) write(*,*)’notthere=’,table%get(’notthere’) ! call print_dict() ! ! delete dictionary entries ! call table%del(’A’) call table%del(’C’) call table%del(’z’) ! a noop as there is no key of ’z’ ! call print_dict() ! ! clear dictionary ! call table%clr() ! call print_dict() ! contains ! subroutine print_dict() integer :: i ! the dictionary is just three arrays write(*,’("DICTIONARY:")’) write(*,’(*(a,"==>","[",a,"]",/))’) & & (trim(table%key(i)), & & table%value(i)(:table%count(i)), & & i=1,size(table%key)) ! end subroutine print_dict ! end program test_dictionary
AUTHOR
John S. Urban
LICENSE
Public Domain
| Nemo Release 3.1 | M_list (3) | July 22, 2023 |
