Binary search in Happy Tree Frame programming language

find_index.htp

frame {
	items: [int]					# implicit input
	value: int						# implicit input
	min_index: int
	max_index: int
	mid_index: int
	<- found_index: int		# explicit output
}

# sel is selector
# seq is sequence
# rep_fail is repeat on fail

tree {
	seq {
		# setup 
		min_index = 0
		max_index = items.count - 1
		sel {
			# Not part of standard binary search algorithm
			# early exit if value is outside of the items range
			# or is equal to min / max value
			seq {
				items[min_index] == value
				found_index = min
			}
			seq {
				items[min_index] > value
				foun_index = -1
			}
			seq {
				items[max_index] == value
				found_index = max
			}
			seq {
				items[max_index] < value
				found_index = -1
			}
			success
		}
		rep_fail {
			sel {
				found_index != null
				seq {
					mid_index = min_index + max_index
					mid_index = mid_index / 2
					items[mid_index] == value
					found_index = mid_index
				}
				seq {
					sel {
						seq {
							items[mid_index] < value
							min_index = mid_index + 1	
						}
						max_index = mid_index - 1
					}
					min_index > max_index
				}
			}
		}
		seq {
			found_index != null
			found_index > -1
		}
	}
}

main.htp

frame {
	values: [int]
	guessed_number: int
	guessed_number_index: int
}

tree {
	seq {
		values = [5, 13, 56, 99]
		rep_fail {
			seq {
				tell "Guess one of the numbers between 1 and 100"
				# using a sub tree to get user input
				readInt {
					guessed_number <- subFrame.value
				}
				sel {
					# using the binary search sub tree
					find_index {
						subFrame.items <- values
						subFrame.value <- guessed_number
						guessed_number_index <- subFrame.found_index
					}
					tell "sorry, that was wrong"
					fail
				}
				tell "Congrats, you found a number"
			}
		}
	}
}