# Lesson #7. Loops. Arbitrary step

## Theory

Lection # 7 in pdf format

### How to use arbitrary step in for loop & loop

Lab 1:

To do: Output all 2-digit odd numbers from 11 to 21.

Expected output:

11  13  15  17  19  21

✍ Algorithm:

• Solution 1. With loop
• Solution 2. With for loop
• for var i:=11 to 21 step(2) do print(i)
{0.4 points} Task 1:
To do: Output the sequence 3 5 7 9 … 21 (from 3 to 21 with a step = 2). Make it twice: with loop and for loop.

The fragment of the program:

begin println('the result with a loop'); var ...; loop ...; ... println('the result with a FOR loop'); for var ... ... end.

Expected output:

the result with a loop
3 5 7 9 11 13 15 17 19 21
the result with a FOR loop
3 5 7 9 11 13 15 17 19 21


[Program name: L7-task-01.pas]

{0.4 points} Task 2:
To do: Output the sequence of integers: 20 18 16 … 2 (from 20 downto 2 with a step = 2). Make it twice: with loop and for loop.

Expected output:

the result with a loop
20 18 16 14 12 10 8 6 4 2
the result with a FOR loop
20 18 16 14 12 10 8 6 4 2


[Program name: L7-task-02.pas]

{0.4 points} Task 3:
To do: Output the sequence of integers: 15 12 9 6 3 0 (from 15 downto 0 with a step = 3). Make it twice: with loop and for loop.

Expected output:

the result with a loop
15 12 9 6 3 0
the result with a FOR loop
15 12 9 6 3 0


[Program name: L7-task-03.pas]

{0.4 points} Task 4:
To do: Output the sequence of integers: 5 10 15 20 … 100 (from 5 to 100). Make it twice: with loop and for loop.

[Program name: L7-task-04.pas]

### Functions z(x)

Lab 2:

To do: Calculate a value of the function z(x) = x3 for all x varying on the interval [1, 7] with a step = 2. Make it twice: with loop and for loop.

Expected output:

the result with a loop
1*1*1 = 1   3*3*3 = 27   5*5*5 = 125   7*7*7 = 343
the result with a FOR loop
1*1*1 = 1   3*3*3 = 27   5*5*5 = 125   7*7*7 = 343


✍ Algorithm:

• Solution:
{0.5 points} Task 5:
To do: Calculate a value of the function z(x) = x2 for all x varying on the interval [3, 12] with a step = 3. Make it twice: with loop and for loop.

Expected output:

the result with a loop
3*3 = 9   6*6 = 36   9*9 = 81   12*12 = 144
the result with a FOR loop
3*3 = 9   6*6 = 36   9*9 = 81   12*12 = 144


[Program name: L7-task-05.pas]

{0.5 points} Task 6:
To do: Calculate a value of the function z(x) = √x for all x varying on the interval [5, 25] with a step = 5. Make it twice: with loop and for loop.

Note: To calculate the square root of a number in pascal there is a standard function sqrt(x), for example:

var result:=sqrt(2); // the result = 1.4142135623731

Expected output:

the result with a loop
sqrt(5) = 2.23606797749979   sqrt(10) = 3.16227766016838
sqrt(15) = 3.87298334620742   sqrt(20) = 4.47213595499958  sqrt(25) = 5
the result with a FOR loop
sqrt(5) = 2.23606797749979   sqrt(10) = 3.16227766016838
sqrt(15) = 3.87298334620742   sqrt(20) = 4.47213595499958  sqrt(25) = 5


[Program name: L7-task-06.pas]

{0.5 points} Task 7:
To do: Calculate a value of the function z(x) = 2x-2 for all x varying on the interval [5, 20] with a step = 3. Make it twice: with loop and for loop.

Expected output:

2*5-2 = 8   2*8-2 = 14   2*11-2 = 20   2*14-2 = 26   2*17-2 = 32  2*20-2 = 38


[Program name: L7-task-07.pas]

{0.5 points} Task 8:
To do: Calculate a value of the function z(x) = sin(x) for all x varying on the interval [1, 5].

Note 1: To calculate the sin() in pascal there is a standard function sin(x), for example:

var result:=sin(2); // the result = 0.909297426825682

Note 2: To output the floating point number with a particular number of digits:

writelnFormat('{0:f2}',3.1415); // output: 3.14

Expected output:

'the rezult of z(x) : '      0.84   0.91   0.14  -0.76  -0.96


[Program name: L7-task-08.pas]

### How to use real step in for & loop

Lab :
To do: Output the sequence: 1.0    1.1   1.2    1.3   1.4    1.5   1.6    1.7  1.8    1.9   2.0.

✍ Algorithm:

• Solution 1. With loop
• Solution 2. With for loop
{0.4 points} Task 9:
To do: Output the sequence 0.1   0.3  0.5   0.7  0.9   1.1. Make it twice: with loop and for loop.

Expected output:

the result with a loop
0.1   0.3   0.5   0.7   0.9   1.1
the result with a FOR loop
0.1   0.3   0.5   0.7   0.9   1.1


[Program name: L7-task-09.pas]

{0.4 points} Task 10:
To do: Output the sequence: 0.0  0.5   1.0  1.5   2.0  2.5. Make it twice: with loop and for loop.

Expected output:

the result with a loop
0.0   0.5   1.0   1.5   2.0   2.5
the result with a FOR loop
0.0   0.5   1.0   1.5   2.0   2.5


[Program name: L7-task-10.pas]

{0.4 points} Task 11:
To do: A real number is given— the price of 1 kg of candy. The program has to output the prices of 1, 2, …, 10 kg of candy. Use for loop.

Note. Use friendly variable names (it’s better to use writelnFormat statement).

Expected output:

'enter a price of 1 kg of candy, please: '
>>> 150.5
the cost of 1 kg = 150.5
the cost of 2 kg = 301
the cost of 3 kg = 451.5
...
the cost of 10 kg = 1505


[Program name: L7-task-11.pas]

{0.4 points} Task 12:
To do: A real number is given— the price of 1 kg of candy. The program has to output the prices of 1.2, 1.4, 1.6 1.8, 2 kg of candy.

Note. Use friendly variable names (it’s better to use writelnFormat statement).

Expected output:

'enter a price of 1 kg of candy, please: '
>>> 100.2
the cost of 1.2 kg =  120.24
the cost of 1.4 kg =  140.28
...
the cost of 2 kg =    200.4


[Program name: L7-task-12.pas]

{0.4 points} Task 13:
To do: Two integers A and B are given. Print the squares of all integers between A and B in ascending order and including these numbers themselves.

Expected output:

'enter two integers, please:  A = , B = '
>>> 1   >>> -2
4, 1, 0, 1

'enter two integers, please:  A = , B = '
>>> 2   >>> 3
4, 9

'enter two integers, please:   A = , B = '
>>> 2   >>> 2
4


[Program name: L7-task-13.pas]

{0.4 points} Task 14:
To do: Two integers A and B are given. Print the square roots of all integers between A and B in ascending order and including these numbers themselves.

Expected output:

'enter two integers, please: A = , B = '
>>> 1   >>> 5
sqrt(1) = 1    sqrt(2) = 1.4142135623731
sqrt(3) = 1.73205080756888    sqrt(4) = 2     sqrt(5) = 2.23606797749979


[Program name: L7-task-14.pas]

Lab:

To do: Using one loop, calculate the value of the sum given by the following formula (N> 0):

Expected output:

Please input real number X
>>> 3
Please input integer N > 0
>>> 5
sum of the sequence = 10.2857142857143


✍ Algorithm:

begin var X := ReadReal('Please input real number X '); var N := ReadInteger('Please input integer N > 0'); Assert(N > 0, 'N<=0'); var sum:=0.0; sum := 0.0; var num1:=-x; var num2:=x; var counter:=1; for var i:=1 to n do begin counter*=i; sum+=(num1+num2)/(i+counter); num1*=-x; num2*=x; end; writeln(\$'sum of the sequence = {sum}'); end.
{0.5 points} Extra task 1:
To do: Using one loop, calculate the value of the sum given by the following formula (N> 0):

Expected output:

Please input real number X
>>> 5
Please input integer N > 0
>>> 2
sum of the sequence = 2.78693528693529


[Program name: L7-extask-1.pas]

{0.5 points} Extra task 2:
To do: Using one loop, calculate the value of the sum given by the following formula (N> 0):

Expected output:

Please input real number X
>>> 5
Please input integer N > 0
>>> 5
sum of the sequence = -491.5


[Program name: L7-extask-2.pas]