The switch statement is used to run a specific set of statements, depending on the value of an expression. It often replaces a set of if…elsif statements giving you more control and readability of your program
Syntax
The syntax of simple switch statement is as follows −
switch expression do
case <val> [, <val-1>....] then
-- Executes when the expression matches one of the values
case <val> [, <val-1>....] then
-- Executes when the expression matches one of the values
.....................
case else
-- Executes when the expression does not matches any case.
end if
The <val> in a case must be either an atom, literal string, constant or enum. Multiple values for a single case can be specified by separating the values by commas. By default, control flows to the end of the switch block when the next case is encountered.
Example
#!/home/euphoria-4.0b2/bin/eui
atom marks = 'C'
switch marks do
case 'A' then
puts(1, "Excellent!\n" )
case 'B', 'C' then
puts(1, "Well done!\n" )
case 'D' then
puts(1, "You passed!\n" )
case 'F' then
puts(1, "Better try again!\n" )
case else
puts(1, "Invalid grade!\n" )
end switch
This produces the following result −
Well done!
The switch…with fallthru Statement
The case statement of a switch is executed when it matches with the given expression value and by default it comes out. By default, control flows to the end of the switch block when the next case is encountered.
The default for a particular switch block can be changed so that control passes to the next executable statement whenever a new case is encountered by using with fallthru in the switch statement −
Syntax
The syntax of simple switch…with fallthru statement is as follows −
switch expression with fallthru do
case <val> [, <val-1>....] then
-- Executes when the expression matches one of the values
break -- optional to come out of the switch from this point.
case <val> [, <val-1>....] then
-- Executes when the expression matches one of the values
break -- Optional to come out of the switch from this point.
.....................
case else
-- Executes when the expression does not matches any case.
break -- Optional to come out of the switch from this point.
end if
Example
#!/home/euphoria-4.0b2/bin/eui
atom marks = 'C'
switch marks with fallthru do
case 'A' then
puts(1, "Excellent!\n" )
case 'B', 'C' then
puts(1, "Well done!\n" )
case 'D' then
puts(1, "You passed!\n" )
case 'F' then
puts(1, "Better try again!\n" )
case else
puts(1, "Invalid grade!\n" )
end switch
This produces the following result −
Well done! You passed! Better try again! Invalid grade!
You can use optional break statement to come out from a point inside a switch statement as follows−
#!/home/euphoria-4.0b2/bin/eui
atom marks = 'C'
switch marks with fallthru do
case 'A' then
puts(1, "Excellent!\n" )
break
case 'B', 'C' then
puts(1, "Well done!\n" )
break
case 'D' then
puts(1, "You passed!\n" )
break
case 'F' then
puts(1, "Better try again!\n" )
break
case else
puts(1, "Invalid grade!\n" )
break
end switch
This produces the following result −
Well done!
The switch….label Statement
The switch statement can have an optional label to name the switch block. This name can be used in nested switch break statements to break out of an enclosing switch rather than just the owning switch.
A switch label is used just to name the block and label names must be double-quoted constant strings having single or multiple words. The label keyword is case-sensitive and should be written as a label.
Syntax
The syntax of simple switch…label statement is as follows −
switch expression label "Label Name" do
case <val> [, <val-1>....] then
-- Executes when the expression matches one of the values
break "LEBEL NAME"
case <val> [, <val-1>....] then
-- Executes when the expression matches one of the values
break "LEBEL NAME"
.....................
case else
-- Executes when the expression does not matches any case.
break "LEBEL NAME"
end if
Example
#!/home/euphoria-4.0b2/bin/eui
atom marks = 'C'
atom scale = 'L'
switch marks label "MARKS" do
case 'A' then
puts(1, "Excellent!\n" )
case 'B', 'C' then
puts(1, "Well done!\n" )
switch scale label "SCALE" do
case 'U' then
puts(1, "Upper scale!\n" )
break "MARKS"
case 'L' then
puts(1, "Lower scale!\n" )
break "MARKS"
case else
puts(1, "Invalid scale!\n" )
break "MARKS"
end switch
case 'D' then
puts(1, "You passed!\n" )
case 'F' then
puts(1, "Better try again!\n" )
case else
puts(1, "Invalid grade!\n" )
end switch
This produces the following result −
Well done! Lower scale!
Note − If you are not using a with fallthru statement then you do not need to use a label because switch statement would come out automatically.
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