REPEAT N TIMES vs REPEAT UNTIL

AP pseudocode gives you two loop types. Python's while and for implement both.

# REPEAT 4 TIMES
for i in range(4):
    print("hello")

# REPEAT UNTIL count >= 10
count = 0
while count < 10:
    count = count + 1

REPEAT 4 TIMES
{
    DISPLAY("hello")
}

count <- 0
REPEAT UNTIL count >= 10
{
    count <- count + 1
}

Common Traps

Infinite loop: Stopping condition never becomes true.
Off-by-one: range(5) gives 0,1,2,3,4 -- 5 iterations ending at 4.
REPEAT UNTIL: Runs while condition is FALSE, stops when TRUE -- opposite intuition from while.

AP exam trap: REPEAT UNTIL stops when the condition becomes TRUE. A while loop in Python runs while the condition is TRUE. These are opposite.

Practice Problems

i <- 1
REPEAT UNTIL i > 5
{
    i <- i + 1
}

total <- 0
REPEAT 4 TIMES
{
    total <- total + 3
}