# Lesson #7. Loops. Arbitrary step

Дата изменения: 8 октября 2020

## 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.

The resulting example:

11  13  15  17  19  21

✍ Algorithm:

• Solution 1. With loop
• Solution 2. With for loop
{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.

[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.

[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.

The resulting example:

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.

The resulting example:

1*1*1 = 1   3*3*3 = 27   5*5*5 = 125   7*7*7 = 343


✍ Algorithm:

• Solution with for loop:
{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.

The resulting example:

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

The resulting example:

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.

The resulting example:

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

The resulting example:

'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.

The resulting example:

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.

The resulting example:

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).

The resulting example:

'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).

The resulting example:

'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.

The resulting example:

'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.

The resulting example:

'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):

The resulting example:

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):

The resulting example:

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):

The resulting example:

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


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

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