! 例題 9-8  成績リストの並べ替え(リスト構造) ［ポインタの活用 ］
PROGRAM ex9_8

  IMPLICIT NONE
  INTEGER :: tensu
  CHARACTER ( LEN = 12 ) :: namae
  TYPE unit
    CHARACTER ( LEN = 12 ) :: name
    INTEGER :: mark
    TYPE ( unit ), POINTER :: next     ! 自分と同じ型の成分をもつ
  END TYPE
  TYPE ( unit ), POINTER :: ent, new, p
  ALLOCATE ( ent )
  NULLIFY( ent%next )                      ! 最初はNULLにしておく

  DO
    PRINT *, 'Input name (or [Enter] only to stop): '
    READ ( *,'( A )' ) namae
    IF ( namae == ' ' ) EXIT
    PRINT *, 'Input her or his mark: '
    READ *, tensu
    CALL rearrange
  END DO

  ! 出力
  p => ent%next
  DO WHILE ( ASSOCIATED ( p ) )           ! NULL となるまで続ける
    PRINT '( A12, I4 )', p%name, p%mark
    p => p%next
  END DO

CONTAINS

SUBROUTINE rearrange

  IMPLICIT NONE

  ALLOCATE ( new )
  p => ent
  DO WHILE ( ASSOCIATED ( p%next ) )        ! (1)(5)
    IF ( tensu > p%next%mark ) EXIT         ! (4)
    p => p%next
  END DO
  new = unit( namae, tensu, p%next )        ! (2)(6)
  p%next => new                             ! (3)(7)

END SUBROUTINE rearrange