until is a looping control structure in Ruby that runs a block of code repeatedly until a specified condition is met. It is the opposite of the while loop, which runs a block of code repeatedly until a condition is no longer met. Here are some examples of how to use until in Ruby:
### Using a boolean condition:
i = 0
until i == 5 do
puts i
i += 1
end
Output:
0
1
2
3
4
In this example, the
until loop will run until the boolean expression i == 5 evaluates to true. The loop will print values of i (from 0 to 4) and increment i until the condition is met.
### Using a negated boolean condition:
count = 10
until !count do
puts count
count -= 1
end
Output:
10
9
8
7
6
5
4
3
2
1
0
In this example, the
count variable is initialized to 10. The until loop will run until the negation of count (which is false for any integer value other than 0) evaluates to true. The loop will print values of count (from 10 to 0) and decrement count until the condition is met.
### Using an inline until statement:
i = 0
puts i += 1 until i == 5
Output:
1
2
3
4
In this example, the
puts statement is executed repeatedly until the condition i == 5 evaluates to true. The loop increments i and prints its value until the condition is met.
### Using begin and end blocks:
i = 0
begin
puts i
i += 1
end until i == 5
Output:
0
1
2
3
4
This example is similar to the first one, but shows how to use
begin and end blocks to group the code statements that need to be repeated in the loop. The loop will run until the condition i == 5 is met.