word_freq.f90 in Fortran

A word-frequency table built from index, substring slices, and a hash-mark chart.

! Count word frequencies in a passage and chart the leaders.
program word_freq
    implicit none
    character(len=*), parameter :: passage = &
        "the rain in maine falls mainly on the plain and " // &
        "the rain stays on the plain"
    character(len=12) :: words(20), current
    integer :: counts(20) = 0
    integer :: used = 0
    integer :: pos, next_space, i
    logical :: known

    ! Walk the passage: cut at each space, tally every word.
    pos = 1
    do while (pos <= len(passage))
        next_space = index(passage(pos:), " ")
        if (next_space == 0) then
            current = passage(pos:)
            pos = len(passage) + 1
        else
            current = passage(pos:pos + next_space - 2)
            pos = pos + next_space
        end if
        if (len_trim(current) == 0) cycle

        known = .false.
        do i = 1, used
            if (words(i) == current) then
                counts(i) = counts(i) + 1
                known = .true.
                exit
            end if
        end do
        if (.not. known) then
            used = used + 1
            words(used) = current
            counts(used) = 1
        end if
    end do

    print '(i0, a)', used, " distinct words"
    print '(a)', "word         ct bar"
    do i = 1, used
        print '(a, 1x, i2, 1x, a)', words(i), counts(i), &
            repeat("#", counts(i))
    end do
end program word_freq

How it works

1. The do while walks the passage, cutting a word at each space with index.
2. A linear search bumps known words or claims the next free slot.
3. repeat("#", counts(i)) draws each word's bar in the report loop.

Keywords and builtins used here

• character
• cycle
• do
• else
• end
• exit
• if
• implicit
• index
• integer
• len
• len_trim
• logical
• none
• not
• parameter
• print
• program
• repeat
• then
• while

The run, in numbers

Lines

47

Characters to type

1084

Tokens

252

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 233 seconds.

Type this snippet

Step 1 of 3 in Encore, step 25 of 27 in Language basics.

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