LinkSort.adb file

with Ada.Text_IO; use Ada.Text_IO;

procedure LinkSort is

  type JobType is (Accountant, Analysist, Manager, Manufacturing, Programmer, Inventory, Sales, SoftwareEnginner);
  package JobTypeIO is new Ada.Text_IO.Enumeration_IO(JobType); use JobTypeIO;

  type EmpName is (Ben, Betty, Bob, Damon, Darlene, David, Desire, Donald, Dustin, Jerry, Kevin, Mary, Marty, Sable, Sam, Sara, Teddy, Tom);
  package EmpNameIO is new Ada.Text_IO.Enumeration_IO(EmpName); use EmpNameIO;

  type LegalResponce is (yup, y, yes, affirmative, nope, no, n, negative);
  subtype PositiveResponce is LegalResponce range yup..affirmative;
  package LegalIO is new Ada.Text_IO.Enumeration_IO(LegalResponce); use LegalIO;

  package IntIO is new Ada.Text_IO.Integer_IO(Integer); use IntIO;

  type Emp is record
    Name: EmpName;
    Job: JobType;
    age: integer;
  end record;

  SortByJob: Array(JobType) of integer := (others =\> 0);

  SortSpace: Array(1..200) of Emp;
  Avail: integer := 1; -- Dynamic storage allocator.
  Pt: integer;

  Again: LegalResponce := affirmative;

begin

  while (Again in PositiveResponce) loop
    put("Enter name: "); get(SortSpace(Avail).Name); --Get emp info.
    put("Enter Job type: "); get(SortSpace(Avail).Job);
    
    -- Insert in appropriate list (by job).
    SortSpace(Avail).Next := SortByJob(SortSpace(Avail).Job);
    SortByJob(SortSpace(Avail).Job) := Avail;
    
    -- Prepare for next dynamically allocated node.
    Avail := Avail + 1; --Using static array allocation as opposed dynamic linked list.
    
    put("Enter another name (yup or nope): "); get(Again);
  end loop;

  -- Sort by job type.

  for I in JobType loop
    new_line; put("Job Type = "); put (I); new_line;
    
    Pt := SortByJob(I); -- Point to first node in job list.
    
    while Pt /= 0 loop
      put(SortSpace(Pt).Name); put(" "); put(SortSpace(Pt).Job);
      put(" link = "); put(SortSpace(Pt).Next,4); new_line;
    
      Pt := SortSpace(Pt).Next; -- Move down list.
    end loop;
  end loop;

end LinkSort;

main.adb file

procedure Main is
begin
  null;
end Main;

Stuck on what I should do next? I've tried to implement everything in the Ada.Text_IO in the main.adb file but errors occurred. I know i need to move something into the main file in order for the program to execute after it has been built. The output statement should be name, job type then sort space number.

We’re not quite done with loops yet. There are still a few things to learn, although some can be left for later. There are certain situations where it is appropriate to use a loop inside another loop. Such a loop is called a nested loop. A nested loop is executed, essentially, from the inside out. Each loop is like a layer and has its own loop control, its own condition and its own loop body. Below is a schematic of three nested loops.

There are many different kinds of nested loops, and they are largely dependent on the underlying algorithm. Below are some examples of the types of nested loops that are possible.

We will consider how a nested loop can be used to create a times table. It basically works by iterating the inner loop 12 times for every iteration of the outer loop. So, 12 × 12 = 144 iterations. The outer loop is highlighted in blue, and the inner loop in red. Here is a sample output:

 1   2   3   4   5   6   7   8   9  10  11  12
 2   4   6   8  10  12  14  16  18  20  22  24
 3   6   9  12  15  18  21  24  27  30  33  36
 4   8  12  16  20  24  28  32  36  40  44  48
 5  10  15  20  25  30  35  40  45  50  55  60
 6  12  18  24  30  36  42  48  54  60  66  72
 7  14  21  28  35  42  49  56  63  70  77  84
 8  16  24  32  40  48  56  64  72  80  88  96
 9  18  27  36  45  54  63  72  81  90  99 108
10  20  30  40  50  60  70  80  90 100 110 120
11  22  33  44  55  66  77  88  99 110 121 132
12  24  36  48  60  72  84  96 108 120 132 144

Ada

with ada.Text_IO; use Ada.Text_IO;
with ada.Integer_Text_IO; use ada.Integer_Text_IO;
procedure nested is 
begin
   for x in 1..12 loop
      for y in 1..12 loop
         put(x*y, width=>4);
      end loop;
      new_line;
   end loop;
end nested;

Fortran

program nested
   integer :: x, y
   do x = 1, 12
      do y = 1, 12
         write(*,10,advance='no') xy
         10 format(I4)
      end do
      write(*,*)
   end do
end program nested

C

#include <stdio.h>
int main(void){
   int x, y;
   for (x=1; x<=12; x=x+1)
   {
      for (y=1; y<=12; y=y+1)
         printf("%4d", x*y);
      printf("\n");
   }
   return 0;
}

Julia

for x = 1:12
   for y = 1:12
      @printf("%4d", x*y)
   end
   println()
end
println(h)

There are of course other loops. These loops are normally used when the number of times a loop iterates isn’t known. These type of loops generally use some form of condition to control the loop. The most prominent type of loop is the while loop. A while loop checks a condition, and if true, processes the code in the loop body, otherwise it exists the loop. Unlike the for loop, which controls the values of the loop index in terms of updating its value, in the loops like while, this process must be added, i.e. the value of i is given the value 1, before the loop is activated, and its value is incremented within the loop body.

We will consider some of these loops using the same Harmonic series, this time in increasing order. The code for the program in Fortran, Ada, Julia and C is shown below. The loop is highlighted in blue.

Fortran

program harmonic
   integer :: n, i
   real :: h

   read (*,*) n
   h = 0
   i = 1
   do while (i <= n)
      h = h + 1.0/i
      i = i + 1
   end do
   write(*,*) h
end program harmonic

Here the index variable, i, must be initiated to the value 1 before the loop begins, and incremented within the loop. The condition states that the loop continues while the value of i is less than or equal to n, i.e. (i <= n) . Fortran also provides a more generic do/end do loop.

C

#include <stdio.h>

int main(void){
   int i, n;
   float h;

   scanf("%d", &n);
   printf("%d\n", n);
   h = 0.0;
   i = 1;
   while (i <= n){
      h = h + 1.0/i;
      i = i + 1;
   }
   printf("%lf\n", h);
   return 0;
}

In the C version, the structure is almost the same, except that the do while of Fortran has been replace with a simple while. With the addition of the statement to increment the value of i, the loop “contents” are now enclosed within { and }. C also has another loop, the do/while() loop, that performs the loop once, then evaluates the condition at the end.

Ada

with ada.Float_Text_IO; use Ada.Float_Text_IO;
with ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure harmonic is
   n, i : integer;
   h : float;
begin
   get(n);
   h := 0.0;
   i := 1;
   while i <= n loop
      h := h + 1.0/float(i);
      i := i + 1;
   end loop;
   put(h);
end harmonic;

In Ada, the while loop looks similar to that of the other to Fortran and C, it is just subtleties in syntax that set them apart. Here there are no parenthesis around the condition. Also note that in the for loop, the index variable, i, did not have to be declared, but here it does. Ada also provides a generic loop/end loop loop.

Julia

n = parse(Int64, chomp(readline()))
println(n)
h = 0
i = 1
while i <= n
   h = h + 1.0/i
   i = i + 1
end
println(h)

Same deal here. Similar to Ada, except the loop keyword after the condition isn’t needed. There are only two loops in Julia.

As you can see, over four languages, the only thing that fundamentally changes is the basic syntax of the loop.

With the basics of for loops, let’s look at an example of an actual program which calculates the Harmonic series, which is an infinite series of the form:

h(n) = 1 + 1/2 + 1/3 + … + 1/n

The code for the program in Fortran, Ada, Julia and C is shown below. The loop is highlighted in blue.  For interest sake, the loops are presented in reverse, i.e. 1/n + 1/(n-1) + … + 1, as it illustrates clearly how each language deals with the simple issue of a decreasing index. In each case the starting value of the index variable i is n, and the ending value is 1. Here it is the algorithm for the Harmonic series depicted visually, clearly showing the role of the loop:

Fortran

program harmonic
   integer :: n, i
   real :: h

   read (*,*) n
   h = 0
   do i = n,1,-1
      h = h + 1.0/i
   end do
   write(*,*) h
end program harmonic

Here the third item (the modifier) in the Fortran loop denotes the type of change to the loop index, in this case, a decrease by 1. In a  normal loop incrementing by 1, the modifier can be omitted.

C

#include <stdio.h>

int main(void){
   int i, n;
   float h;

   scanf("%d", &n);
   printf("%d\n", n);
   h = 0.0;
   for (i=n; i>=1; i=i-1)
      h = h + 1.0/i;
   printf("%lf\n", h);
   return 0;
}

In the C version, the loop index is decremented using the statement i=i–1. For more than one statement after the for loop definition, the statements would have to be encapsulated in { and }.

Ada

with ada.Float_Text_IO; use Ada.Float_Text_IO;
with ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure harmonic is
   n : integer;
   h : float;
begin
   get(n);
   h := 0.0;
   for i in reverse 1..n loop
      h := h + 1.0/float(i);
   end loop;
   put(h);
end harmonic;

In Ada, the keyword reverse is used to specify a loop will be decreasing in value.

Julia

n = parse(Int64, chomp(readline()))
println(n)
h = 0
for i = n:-1:1
   h = h + 1.0/i
end
println(h)

Here the index modifier is placed in the centre, n:-1:1, implying i has the values n to 1, modified by -1 each loop iteration. In a  normal loop incrementing by 1, the modifier can be omitted.

Humans are, by nature, repetitive beings. Watch the Star Trek: TNG episode “Cause and Effect”, and you will quickly understand what a loop is as the Enterprise is caught in a causality time loop. There are also times when programs must do a task more than once. If the repetition is limited to some countable number of recurrences with a foreseeable end then it is called a loop. And if, at least in the perception of the individual who is experiencing a certain situation, there is no end in sight then one is talking about endless or infinite loops. All of the above can be desirable or not. Here is a visual illustration:

The code in the program moves linearly from statement A, until it encounters a loop. At the start of the loop, the loop control tests some condition. If the condition is true, then the loop activates the piece of code (made up of one or more statements) in what is called the loop body. When that code is done the loop returns to the loop control, and the process starts all over. If the condition in the loop control becomes false, nothing happens, and the program ends the loop, and continues on to statement B. There is also a possibility that the first time into the loop, the condition becomes false, and in that case the loop is bypassed.

Loops are structures that allow for repetition – repeating an activity a number of times. There are different kinds of repetition:

1. Loops where the number of repetitions is known before the loop activates.
2. Loops where the number of repetitions isn’t known, and is controlled by some condition.
3. Loops that are infinite, i.e. could continue to infinity and beyond.

The best example of the first case encountered in most languages is the for loop. Here we use a variable called a loop index to control the loop. Each time a loop loops it is called an iteration. So if the loop index is x, and it repeats 100 times, then x will begin with a value of 1, and increment by 1 each iteration, until x reaches 100. In Julia this is easily achieved in the following manner (in this case the loop simply prints out each value of x):

for x = 1:100
   println(x)
end

In Ada it takes a similar format (the printing part is a little different, but just ignore that bit):

for x in 1..100 loop
    put(x); 
    new_line;
end loop;

Ada uses the keyword loop to signify it as a loop. Fortran also uses a similar construct, but has never used the for loop, opting instead for the keyword do. Same concept, different name.

do x = 1, 100
   write(*,*) x
end do

C also uses a for loop, although it can be somewhat more convoluted:

for (x=1; x<=100; x=x+1)
   printf("%d\n",x);

All have their varied syntax, but achieve the same goal – a known number of iterations.

We’re not quite done with loops yet. There are still a few things to learn, although some can be left for later. There are certain situations where it is appropriate to use a loop inside another loop. Such a loop is called a nested loop. A nested loop is executed, essentially, from the inside out. Each loop is like a layer and has its own loop control, its own condition and its own loop body. Below is a schematic of three nested loops.

There are many different kinds of nested loops, and they are largely dependent on the underlying algorithm. Below are some examples of the types of nested loops that are possible.

We will consider how a nested loop can be used to create a times table. It basically works by iterating the inner loop 12 times for every iteration of the outer loop. So, 12 × 12 = 144 iterations. The outer loop is highlighted in blue, and the inner loop in red. Here is a sample output:

 1   2   3   4   5   6   7   8   9  10  11  12
 2   4   6   8  10  12  14  16  18  20  22  24
 3   6   9  12  15  18  21  24  27  30  33  36
 4   8  12  16  20  24  28  32  36  40  44  48
 5  10  15  20  25  30  35  40  45  50  55  60
 6  12  18  24  30  36  42  48  54  60  66  72
 7  14  21  28  35  42  49  56  63  70  77  84
 8  16  24  32  40  48  56  64  72  80  88  96
 9  18  27  36  45  54  63  72  81  90  99 108
10  20  30  40  50  60  70  80  90 100 110 120
11  22  33  44  55  66  77  88  99 110 121 132
12  24  36  48  60  72  84  96 108 120 132 144

Ada

with ada.Text_IO; use Ada.Text_IO;
with ada.Integer_Text_IO; use ada.Integer_Text_IO;
procedure nested is 
begin
   for x in 1..12 loop
      for y in 1..12 loop
         put(x*y, width=>4);
      end loop;
      new_line;
   end loop;
end nested;

Fortran

program nested
   integer :: x, y
   do x = 1, 12
      do y = 1, 12
         write(*,10,advance='no') xy
         10 format(I4)
      end do
      write(*,*)
   end do
end program nested

C

#include <stdio.h>
int main(void){
   int x, y;
   for (x=1; x<=12; x=x+1)
   {
      for (y=1; y<=12; y=y+1)
         printf("%4d", x*y);
      printf("\n");
   }
   return 0;
}

Julia

for x = 1:12
   for y = 1:12
      @printf("%4d", x*y)
   end
   println()
end
println(h)

There are of course other loops. These loops are normally used when the number of times a loop iterates isn’t known. These type of loops generally use some form of condition to control the loop. The most prominent type of loop is the while loop. A while loop checks a condition, and if true, processes the code in the loop body, otherwise it exists the loop. Unlike the for loop, which controls the values of the loop index in terms of updating its value, in the loops like while, this process must be added, i.e. the value of i is given the value 1, before the loop is activated, and its value is incremented within the loop body.

We will consider some of these loops using the same Harmonic series, this time in increasing order. The code for the program in Fortran, Ada, Julia and C is shown below. The loop is highlighted in blue.

Fortran

program harmonic
   integer :: n, i
   real :: h

   read (*,*) n
   h = 0
   i = 1
   do while (i <= n)
      h = h + 1.0/i
      i = i + 1
   end do
   write(*,*) h
end program harmonic

Here the index variable, i, must be initiated to the value 1 before the loop begins, and incremented within the loop. The condition states that the loop continues while the value of i is less than or equal to n, i.e. (i <= n) . Fortran also provides a more generic do/end do loop.

C

#include <stdio.h>

int main(void){
   int i, n;
   float h;

   scanf("%d", &n);
   printf("%d\n", n);
   h = 0.0;
   i = 1;
   while (i <= n){
      h = h + 1.0/i;
      i = i + 1;
   }
   printf("%lf\n", h);
   return 0;
}

In the C version, the structure is almost the same, except that the do while of Fortran has been replace with a simple while. With the addition of the statement to increment the value of i, the loop “contents” are now enclosed within { and }. C also has another loop, the do/while() loop, that performs the loop once, then evaluates the condition at the end.

Ada

with ada.Float_Text_IO; use Ada.Float_Text_IO;
with ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure harmonic is
   n, i : integer;
   h : float;
begin
   get(n);
   h := 0.0;
   i := 1;
   while i <= n loop
      h := h + 1.0/float(i);
      i := i + 1;
   end loop;
   put(h);
end harmonic;

In Ada, the while loop looks similar to that of the other to Fortran and C, it is just subtleties in syntax that set them apart. Here there are no parenthesis around the condition. Also note that in the for loop, the index variable, i, did not have to be declared, but here it does. Ada also provides a generic loop/end loop loop.

Julia

n = parse(Int64, chomp(readline()))
println(n)
h = 0
i = 1
while i <= n
   h = h + 1.0/i
   i = i + 1
end
println(h)

Same deal here. Similar to Ada, except the loop keyword after the condition isn’t needed. There are only two loops in Julia.

As you can see, over four languages, the only thing that fundamentally changes is the basic syntax of the loop.

With the basics of for loops, let’s look at an example of an actual program which calculates the Harmonic series, which is an infinite series of the form:

h(n) = 1 + 1/2 + 1/3 + … + 1/n

The code for the program in Fortran, Ada, Julia and C is shown below. The loop is highlighted in blue.  For interest sake, the loops are presented in reverse, i.e. 1/n + 1/(n-1) + … + 1, as it illustrates clearly how each language deals with the simple issue of a decreasing index. In each case the starting value of the index variable i is n, and the ending value is 1. Here it is the algorithm for the Harmonic series depicted visually, clearly showing the role of the loop:

Fortran

program harmonic
   integer :: n, i
   real :: h

   read (*,*) n
   h = 0
   do i = n,1,-1
      h = h + 1.0/i
   end do
   write(*,*) h
end program harmonic

Here the third item (the modifier) in the Fortran loop denotes the type of change to the loop index, in this case, a decrease by 1. In a  normal loop incrementing by 1, the modifier can be omitted.

C

#include <stdio.h>

int main(void){
   int i, n;
   float h;

   scanf("%d", &n);
   printf("%d\n", n);
   h = 0.0;
   for (i=n; i>=1; i=i-1)
      h = h + 1.0/i;
   printf("%lf\n", h);
   return 0;
}

In the C version, the loop index is decremented using the statement i=i–1. For more than one statement after the for loop definition, the statements would have to be encapsulated in { and }.

Ada

with ada.Float_Text_IO; use Ada.Float_Text_IO;
with ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure harmonic is
   n : integer;
   h : float;
begin
   get(n);
   h := 0.0;
   for i in reverse 1..n loop
      h := h + 1.0/float(i);
   end loop;
   put(h);
end harmonic;

In Ada, the keyword reverse is used to specify a loop will be decreasing in value.

Julia

n = parse(Int64, chomp(readline()))
println(n)
h = 0
for i = n:-1:1
   h = h + 1.0/i
end
println(h)

Here the index modifier is placed in the centre, n:-1:1, implying i has the values n to 1, modified by -1 each loop iteration. In a  normal loop incrementing by 1, the modifier can be omitted.

Humans are, by nature, repetitive beings. Watch the Star Trek: TNG episode “Cause and Effect”, and you will quickly understand what a loop is as the Enterprise is caught in a causality time loop. There are also times when programs must do a task more than once. If the repetition is limited to some countable number of recurrences with a foreseeable end then it is called a loop. And if, at least in the perception of the individual who is experiencing a certain situation, there is no end in sight then one is talking about endless or infinite loops. All of the above can be desirable or not. Here is a visual illustration:

The code in the program moves linearly from statement A, until it encounters a loop. At the start of the loop, the loop control tests some condition. If the condition is true, then the loop activates the piece of code (made up of one or more statements) in what is called the loop body. When that code is done the loop returns to the loop control, and the process starts all over. If the condition in the loop control becomes false, nothing happens, and the program ends the loop, and continues on to statement B. There is also a possibility that the first time into the loop, the condition becomes false, and in that case the loop is bypassed.

Loops are structures that allow for repetition – repeating an activity a number of times. There are different kinds of repetition:

1. Loops where the number of repetitions is known before the loop activates.
2. Loops where the number of repetitions isn’t known, and is controlled by some condition.
3. Loops that are infinite, i.e. could continue to infinity and beyond.

The best example of the first case encountered in most languages is the for loop. Here we use a variable called a loop index to control the loop. Each time a loop loops it is called an iteration. So if the loop index is x, and it repeats 100 times, then x will begin with a value of 1, and increment by 1 each iteration, until x reaches 100. In Julia this is easily achieved in the following manner (in this case the loop simply prints out each value of x):

for x = 1:100
   println(x)
end

In Ada it takes a similar format (the printing part is a little different, but just ignore that bit):

for x in 1..100 loop
    put(x); 
    new_line;
end loop;

Ada uses the keyword loop to signify it as a loop. Fortran also uses a similar construct, but has never used the for loop, opting instead for the keyword do. Same concept, different name.

do x = 1, 100
   write(*,*) x
end do

C also uses a for loop, although it can be somewhat more convoluted:

for (x=1; x<=100; x=x+1)
   printf("%d\n",x);

All have their varied syntax, but achieve the same goal – a known number of iterations.