Difference between revisions of "Ruby/C2/Logical-and-other-Operators/English-timed"

| Welcome to this spoken tutorial on '''Logical & Other Operators. '''

| In this tutorial we will learn  

| '''Range Operators '''

|Here we are using  

| '''Ubuntu Linux''' version 12.04  

| ''' Ruby 1.9.3  '''

|To follow this tutorial you must know how to use ''' Terminal''' and '''Text editor''' in ''' Linux'''.  

|You must also be familiar with '''irb'''  

| If not, for relevant tutorials, please visit our website  

|Logical Operators are also known as ''' Boolean Operators'''

|'''Logical Operators''' are,

| ''' double ampersand (&&)'''  that is '''(and)'''  

| ''' double pipe '''  that is '''(or)'''  

|''' Exclamation (!)'''  that is '''(not)'''  

| '''&&(double ampersand)''' and '''and''' evaluate to '''true''' only if both the expressions are '''true.'''  

|Second expression is evaluated only if the first is '''true. '''  

| Difference in the two forms is, precedence

|Let's us see some examples now.  

|  Open the ''' terminal''' by pressing '''Ctrl, Alt and T''' keys simultaneously.  

|Type '''irb''' and press '''Enter''' to launch '''interactive Ruby'''

| Type ''' 3 greater than 2 space double ampersand space 4 less than 5'''  

| Press ''' Enter'''

| We get the output as '''true.'''

|Here, '''expression1'''  that is 3>2 is '''true'''.  

|'''Expression 2''' that is 4<5 is also '''true.'''  

|Now press '''Up Arrow''' key to get the previous command.  

| And ''' replace the double ampersand''' symbol with the word ''' and.'''

|  Press '''Enter '''

| Now press up arrow key again to get the previous command.  

| In ''' expression 1''' replace '''greater than''' sign with '''less than'''

|Press ''' Enter '''

| We get the output as '''false.'''

|This is because ''' 3<2''' is '''false.'''

| So, we get output as '''false.'''

| ''' double pipe''' and '''or''' evaluate to '''true''', if either '''expression''' is '''true.'''  

|Symbolic '''or''' i.e ''' double pipe''' has higher '''precedence.'''  

|''' 10 greater than 6 space double pipe space 12 less than 7'''

|We get output as '''true.'''

|Here '''expression 1''' that is '''10>6''' is '''true'''.

| Since the first expression is '''true''' , second expression will not be evaluated.  

|  Now press the '''Up Arrow''' key to get the previous command.  

|  In '''expression 1''' replace '''greater than sign''' with '''less than sign.'''

|  And replace '''pipe''' symbol with the word '''or.'''  

|  Since both the expressions are '''false''', we get output as '''false. '''

|'''! (exclamation mark )''' and '''not''' operators return the opposite value of the expression  

|  If the '''expression''' is '''true''', '''exclamation mark'''  operator will return a '''false''' value.  

| Difference in the two forms is '''precedence. '''

| Symbolic '''not that is (!)''' has higher '''precedence.'''  

| Let's try out the '''not''' operator.  

|First type ''' 10 double equal to 10'''

|  Press '''Enter '''

|We get the output as '''true.'''

|To invert the result of above expression,  

| let's add the '''not''' operator before the expression.  

|Type '''Exclamation mark within brackets 10 double equal to 10 '''

|We get the output as '''false.'''

|Next, let us learn about '''parallel assignment. '''

|Let's declare three variables '''a, b, c''' using '''parallel assignment. '''

| Type '''a comma b comma c equal to 10 comma 20 comma 30 '''

|Here, '''10''' will be assigned to variable '''a '''

|'''20''' will be assigned to variable '''b '''

|'''30''' will be assigned to variable '''c '''

|The right hand side acts as an '''array'''.  

|If we list multiple variables on the left hand side,  then the array is unpacked and assigned into the respective variables.  

|We will learn about '''arrays''' in detail in the upcoming tutorials.  

| For now, let's check whether the '''assignment''' is done properly.  

| Type '''a''' and press '''Enter.'''

|Value '''10''' stored in variable '''a''' is displayed.  

|Type '''b''' and press '''Enter.'''

|We get 20  

| Type '''c''' and press '''Enter.'''

|30 is displayed.  

|Let us swap the values of variables a and b.

|Type '''puts space within double quotes a equal to hash within curly brackets a comma within double quotes b equal to hash within curly brackets b'''  

| We get the output as '''a=10 '''

|'''b=20 '''

|Now let's swap a and b.

|To do so type  

| Press '''Up Arrow''' key twice to get the '''puts''' command and press '''Enter.'''

|  We get the output as  

| '''b=10 '''

|The values in a '''range''' can be numbers, characters, strings or objects.  

|'''Ranges''' are used to identify whether a value falls within a particular range, too.  

|Type '''Within brackets 1 two dots 10 then dot to underscore a '''

|'''Inclusive operator''' includes both begin and end values in a range.  

|Here '''to_a''' method is used to convert a '''range''' to a list.  

|Here you can see the values 1 and 10 are included in the range.  

|Now we will see an '''exclusive range''' operator.  

|Type  '''Within brackets 1 three dots 10 then dot to underscore a '''

|Here the end value 10 is not included in the range.  

|Now let's check whether 5 lies in the range of 1 to 10.  

|Type '''Within brackets 1 two dots 10 three times equal to and then 5 '''

|'''Equality operator''' is used to check whether a value lies in the range.  

|We get the output as '''true''' since 5 lies in the range 1 to 10.  

|In this tutorial, we have learnt  

|'''Logical operator''' i.e ''' double ampersand, double pipe and exclamation mark operators '''

|'''Parallel assignment''' Ex: a,b,c=10,20,30  

|'''Range Operator Inclusive operator '''(..) and Exclusive operator(...)'''

|As an assignment  

|Declare two variables using '''parallel assignment''' and  

|Check whether their sum lies between 20 and 50  

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|And this is Shalini Nair signing off  Thank you