Language

Control Flow

print, if, for, and the repeat loops

Statements are evaluated for their side effects. Control-flow statements decide what runs and how often.

Quick reference

print(x)
if cond print('foo') else print('bar') end
for x in 'foo' print(x) end
for x in 'foo' index i print(i) end
repeat 3 times print(it) end
repeat while x < 3 x = x + 1 end
repeat until x >= 3 x = x + 1 end
break
continue

print

print(x)

if

if true
  print('foo')
else
  print('bar')
end

The else branch is optional:

if true
  print('foo')
end

for

for iterates over any iterable: lists, strings (per character), and maps.

for x in 'foo'
  print(x)
end

That prints f, o, o on separate lines.

The optional index clause binds the iteration index:

for x in 'foo' index i
  print(i)
  print(x)
end

The loop variable does not escape the loop - see Variables & Scope.

repeat

repeat has three forms. repeat N times runs a block N times, binding the current count to it:

repeat 3 times
  print(it)
end

repeat while runs as long as its predicate holds; repeat until runs until the predicate becomes true:

repeat while x < 3
  x = x + 1
end

repeat until x >= 3
  x = x + 1
end

The condition and body can share a line (repeat while x < 3 x = x + 1 end), but putting the body on its own line reads more clearly.

Inside any loop, break exits and continue skips to the next iteration:

break
continue

Blocks

A block is a sequence of statements terminated by end. The if, for, and repeat forms above all use blocks.

See also