The Ring programming language version 1.3 book - Part 11 of 88
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The document summarizes control structures in Ring programming language including branching statements like if/else and switch statements, looping statements like while, for, for-in loops. It describes the syntax and provides examples to explain if/else, switch, while, for, for-in loops. It also covers concepts like do-again loop, exit and loop commands to exit/continue loops, short-circuit evaluation in logical operators and, or and using comments inside code.
![Ring Documentation, Release 1.3
list = [1,2,3,"four","five"]
list2 = list
list = []
See list # print the first list - no items to print
See "********" + nl
See list2 # print the second list - contains 5 items
14.3 Weakly Typed
Ring is a weakly typed language, this means that the language can automatically convert between data types (like
string & numbers) when that conversion make sense.
Rules:
<NUMBER> + <STRING> --> <NUMBER>
<STRING> + <NUMBER> --> <STRING>
Note: The same operator ‘+’ can be used as an arithmetic operator or for string concatenation.
Example:
x = 10 # x is a number
y = "20" # y is a string
sum = x + y # sum is a number (y will be converted to a number)
Msg = "Sum = " + sum # Msg is a string (sum will be converted to a string)
see Msg + nl
14.3. Weakly Typed 78](https://image.slidesharecdn.com/101ringring-170612194219/85/The-Ring-programming-language-version-1-3-book-Part-11-of-88-1-320.jpg)
![Ring Documentation, Release 1.3
15.4 Bitwise Operators
The next table presents all of the bitwise operators provided by the Ring language. Assume variable X=8 and variable
Y=2 then:
Operator Description Example Result
& Binary AND x & y 0
| Binary OR x | y 10
^ Binary XOR x ^ y 10
~ Binary Ones Complement ~x -9
<< Binary Left Shift x << y 32
>> Binary Right Shift x >> y 2
15.5 Assignment Operators
The next table presents all of the assignment operators provided by the Ring language.
Assume variable X=8 then:
Operator Description Example Result
= Assignment x = 10 x=10
+= Add AND assignment x += 5 x=13
-= Subtract AND assignment x -= 3 x=5
*= Multiply AND assignment x *= 2 x=16
/= Divide AND assignment x /= 3 x=2.67
%= Modulus AND assignment x %= 2 x=0
<<= Left shift AND assignment x <<= 2 x=32
>>= Right shift AND assignment x >>= 2 x=2
&= Bitwise AND assignment x &= 4 x=0
|= Bitwise OR and assignment x |= 3 x=11
^= Bitwise XOR and assignment x ^= 4 x=12
15.6 Misc Operators
Operator Description
:literal using : before identifier mean literal
Start:End create list contains items from start to end
[list items] define list items
list[index] access list item
obj.name using the dot operator to access object members (attributes/methods).
obj {stmts} execute statements with direct access to object attributes & methods
func(para,...) call function using parameters separated by comma
15.7 Operators Precedence
The next table present operators from higher precedence (Evaluated first) to lower precedence.
15.4. Bitwise Operators 80](https://image.slidesharecdn.com/101ringring-170612194219/85/The-Ring-programming-language-version-1-3-book-Part-11-of-88-3-320.jpg)
![Ring Documentation, Release 1.3
Operator
. [] () {}
- ~ :Literal [list items]
++ - -
Start:End
* / %
+ -
<< >>
&
| ^
< > <= >=
= !=
not
and or
Assignment = += -= *= /= %=>>= <<= &= ^= |=
Example:
See 3+5*4 # prints 23
15.7. Operators Precedence 81](https://image.slidesharecdn.com/101ringring-170612194219/85/The-Ring-programming-language-version-1-3-book-Part-11-of-88-4-320.jpg)
![Ring Documentation, Release 1.3
for identifier=expression to expression [step expression]
Block of statements
next
Example:
# print numbers from 1 to 10
for x = 1 to 10 see x + nl next
Example:
# Dynamic loop
See "Start : " give nStart
See "End : " give nEnd
See "Step : " give nStep
For x = nStart to nEnd Step nStep
see x + nl
Next
Example:
# print even numbers from 0 to 10
for x = 0 to 10 step 2
see x + nl
next
Example:
# print even numbers from 10 to 0
for x = 10 to 0 step -2
see x + nl
next
• For in Loop
Syntax:
for identifier in List/String [step expression]
Block of statements
next
Example:
aList = 1:10 # create list contains numbers from 1 to 10
for x in aList see x + nl next # print numbers from 1 to 10
16.3 Using The Step option with For in
We can use the Step option with For in to skip number of items in each iteration
Example:
aList = 1:10 # create list contains numbers from 1 to 10
# print odd items inside the list
for x in aList step 2
see x + nl
next
16.3. Using The Step option with For in 84](https://image.slidesharecdn.com/101ringring-170612194219/85/The-Ring-programming-language-version-1-3-book-Part-11-of-88-7-320.jpg)
![Ring Documentation, Release 1.3
16.4 Using For in to modify lists
When we use (For in) we get items by reference.
This means that we can read/edit items inside the loop.
Example:
aList = 1:5 # create list contains numbers from 1 to 5
# replace list numbers with strings
for x in aList
switch x
on 1 x = "one"
on 2 x = "two"
on 3 x = "three"
on 4 x = "four"
on 5 x = "five"
off
next
see aList # print the list items
16.5 Do Again Loop
Syntax:
do
Block of statements
again expression
Example:
x = 1
do
see x + nl
x++
again x <= 10
16.6 Exit Command
Used to go outside one or more of loops.
Syntax:
exit [expression] # inside loop
Example:
for x = 1 to 10
see x + nl
if x = 5 exit ok
next
16.4. Using For in to modify lists 85](https://image.slidesharecdn.com/101ringring-170612194219/85/The-Ring-programming-language-version-1-3-book-Part-11-of-88-8-320.jpg)
![Ring Documentation, Release 1.3
16.7 Exit from two loops
The next example presents how to use the exit command to exit from two loops in one jump.
Example:
for x = 1 to 10
for y = 1 to 10
see "x=" + x + " y=" + y + nl
if x = 3 and y = 5
exit 2 # exit from 2 loops
ok
next
next
• Loop Command
Used to jump to the next iteration in the loop.
Syntax:
loop [expression] # inside loop
Example:
for x = 1 to 10
if x = 3
see "Number Three" + nl
loop
ok
see x + nl
next
16.8 Exit/Loop inside sub functions
While we are inside a loop, we can call a function then use the exit and/or loop command inside that function and the
command will work on the outer loop.
Example:
# print numbers from 1 to 10 except number 5.
for x = 1 to 10
ignore(x,5)
see x + nl
next
func ignore x,y
if x = y
loop
ok
16.9 Short-circuit evaluation
The logical operators and/or follow the short-circuit evaluation.
16.7. Exit from two loops 86](https://image.slidesharecdn.com/101ringring-170612194219/85/The-Ring-programming-language-version-1-3-book-Part-11-of-88-9-320.jpg)
The Ring programming language version 1.3 book - Part 11 of 88
- 1. Ring Documentation, Release 1.3 list = [1,2,3,"four","five"] list2 = list list = [] See list # print the first list - no items to print See "********" + nl See list2 # print the second list - contains 5 items 14.3 Weakly Typed Ring is a weakly typed language, this means that the language can automatically convert between data types (like string & numbers) when that conversion make sense. Rules: <NUMBER> + <STRING> --> <NUMBER> <STRING> + <NUMBER> --> <STRING> Note: The same operator ‘+’ can be used as an arithmetic operator or for string concatenation. Example: x = 10 # x is a number y = "20" # y is a string sum = x + y # sum is a number (y will be converted to a number) Msg = "Sum = " + sum # Msg is a string (sum will be converted to a string) see Msg + nl 14.3. Weakly Typed 78
- 2. CHAPTER FIFTEEN OPERATORS In this chapter we will introduce the operators provided by the Ring programming langauge. 15.1 Arithmetic Operators The next table presents all of the arithmetic operators provided by the Ring language. Assume variable X=50 and variable Y=10 then: Operator Description Example Result + Add x+y 60 - Subtract x-y 40 * Multiplies x*y 500 / Divide x/y 5 % Modulus x%y 0 ++ Increment x++ 51 - - Decrement x- - 49 15.2 Relational Operators The next table presents all of the relational operators provided by the Ring language. Assume variable X=50 and variable Y=10 then: Operator Description Example Result = Equal x = y False != Not Equal x != y True > Greater than x > y True < Less than x < y False >= Greater or Equal x >= y True <= Less than or Equal x <= y False 15.3 Logical Operators The next table presents all of the logical operators provided by the Ring language. Assume variable X=True and variable Y=False then: Operator Description Example Result and Logical AND x and y False or Logical OR x or y True not Logical Not not x False 79
- 3. Ring Documentation, Release 1.3 15.4 Bitwise Operators The next table presents all of the bitwise operators provided by the Ring language. Assume variable X=8 and variable Y=2 then: Operator Description Example Result & Binary AND x & y 0 | Binary OR x | y 10 ^ Binary XOR x ^ y 10 ~ Binary Ones Complement ~x -9 << Binary Left Shift x << y 32 >> Binary Right Shift x >> y 2 15.5 Assignment Operators The next table presents all of the assignment operators provided by the Ring language. Assume variable X=8 then: Operator Description Example Result = Assignment x = 10 x=10 += Add AND assignment x += 5 x=13 -= Subtract AND assignment x -= 3 x=5 *= Multiply AND assignment x *= 2 x=16 /= Divide AND assignment x /= 3 x=2.67 %= Modulus AND assignment x %= 2 x=0 <<= Left shift AND assignment x <<= 2 x=32 >>= Right shift AND assignment x >>= 2 x=2 &= Bitwise AND assignment x &= 4 x=0 |= Bitwise OR and assignment x |= 3 x=11 ^= Bitwise XOR and assignment x ^= 4 x=12 15.6 Misc Operators Operator Description :literal using : before identifier mean literal Start:End create list contains items from start to end [list items] define list items list[index] access list item obj.name using the dot operator to access object members (attributes/methods). obj {stmts} execute statements with direct access to object attributes & methods func(para,...) call function using parameters separated by comma 15.7 Operators Precedence The next table present operators from higher precedence (Evaluated first) to lower precedence. 15.4. Bitwise Operators 80
- 4. Ring Documentation, Release 1.3 Operator . [] () {} - ~ :Literal [list items] ++ - - Start:End * / % + - << >> & | ^ < > <= >= = != not and or Assignment = += -= *= /= %=>>= <<= &= ^= |= Example: See 3+5*4 # prints 23 15.7. Operators Precedence 81
- 5. CHAPTER SIXTEEN CONTROL STRUCTURES - FIRST STYLE In this chapter we are going to learn about the control structures provided by the Ring programming language. 16.1 Branching • If Statement Syntax: if Expression Block of statements but Expression Block of statements else Block of statements ok Example: see " Main Menu --------- (1) Say Hello (2) About (3) Exit " give nOption if nOption = 1 see "Enter your name : " give name see "Hello " + name + nl but nOption = 2 see "Sample : using if statement" + nl but nOption = 3 bye else see "bad option..." + nl ok • Switch Statement Syntax: switch Expression on Expression Block of statements other Block of statements off 82
- 6. Ring Documentation, Release 1.3 Example: See " Main Menu --------- (1) Say Hello (2) About (3) Exit " Give nOption Switch nOption On 1 See "Enter your name : " Give name See "Hello " + name + nl On 2 See "Sample : using switch statement" + nl On 3 Bye Other See "bad option..." + nl Off 16.2 Looping • While Loop Syntax: while Expression Block of statements end Example: While True See " Main Menu --------- (1) Say Hello (2) About (3) Exit " Give nOption Switch nOption On 1 See "Enter your name : " Give name See "Hello " + name + nl On 2 See "Sample : using while loop" + nl On 3 Bye Other See "bad option..." + nl Off End • For Loop Syntax: 16.2. Looping 83
- 7. Ring Documentation, Release 1.3 for identifier=expression to expression [step expression] Block of statements next Example: # print numbers from 1 to 10 for x = 1 to 10 see x + nl next Example: # Dynamic loop See "Start : " give nStart See "End : " give nEnd See "Step : " give nStep For x = nStart to nEnd Step nStep see x + nl Next Example: # print even numbers from 0 to 10 for x = 0 to 10 step 2 see x + nl next Example: # print even numbers from 10 to 0 for x = 10 to 0 step -2 see x + nl next • For in Loop Syntax: for identifier in List/String [step expression] Block of statements next Example: aList = 1:10 # create list contains numbers from 1 to 10 for x in aList see x + nl next # print numbers from 1 to 10 16.3 Using The Step option with For in We can use the Step option with For in to skip number of items in each iteration Example: aList = 1:10 # create list contains numbers from 1 to 10 # print odd items inside the list for x in aList step 2 see x + nl next 16.3. Using The Step option with For in 84
- 8. Ring Documentation, Release 1.3 16.4 Using For in to modify lists When we use (For in) we get items by reference. This means that we can read/edit items inside the loop. Example: aList = 1:5 # create list contains numbers from 1 to 5 # replace list numbers with strings for x in aList switch x on 1 x = "one" on 2 x = "two" on 3 x = "three" on 4 x = "four" on 5 x = "five" off next see aList # print the list items 16.5 Do Again Loop Syntax: do Block of statements again expression Example: x = 1 do see x + nl x++ again x <= 10 16.6 Exit Command Used to go outside one or more of loops. Syntax: exit [expression] # inside loop Example: for x = 1 to 10 see x + nl if x = 5 exit ok next 16.4. Using For in to modify lists 85
- 9. Ring Documentation, Release 1.3 16.7 Exit from two loops The next example presents how to use the exit command to exit from two loops in one jump. Example: for x = 1 to 10 for y = 1 to 10 see "x=" + x + " y=" + y + nl if x = 3 and y = 5 exit 2 # exit from 2 loops ok next next • Loop Command Used to jump to the next iteration in the loop. Syntax: loop [expression] # inside loop Example: for x = 1 to 10 if x = 3 see "Number Three" + nl loop ok see x + nl next 16.8 Exit/Loop inside sub functions While we are inside a loop, we can call a function then use the exit and/or loop command inside that function and the command will work on the outer loop. Example: # print numbers from 1 to 10 except number 5. for x = 1 to 10 ignore(x,5) see x + nl next func ignore x,y if x = y loop ok 16.9 Short-circuit evaluation The logical operators and/or follow the short-circuit evaluation. 16.7. Exit from two loops 86
- 10. Ring Documentation, Release 1.3 If the first argument of the AND operator is zero, then there is no need to evaluate the second argument and the result will be zero. If the first argument of the OR operator is one, then there is no need to evaluate the second argument and the result will be one. Example: /* output ** nice ** nice ** great */ x = 0 y = 10 if (x = 0 and nice()) and (y = 10 and nice()) see "great" + nl ok func nice see "nice" + nl return 1 Example: # No output x = 0 y = 10 if (x = 1 and nice()) and (y = 10 and nice()) see "great" + nl ok func nice see "nice" + nl return 1 Example: /* output ** nice ** great */ x = 0 y = 10 if (x = 0 and nice()) or (y = 10 and nice()) see "great" + nl ok func nice see "nice" + nl return 1 16.10 Comments about evaluation • True, False, nl & NULL are variables defined by the language • True = 1 • False = 0 • nl = new line • NULL = empty string = “” 16.10. Comments about evaluation 87