Control Flow

If Statement#

If <condition> then, <statement>.

With else:

If <condition> then, <statement>. Otherwise, <statement>.

With else-if:

If <condition> then, <statement>. But if <condition> then, <statement>. Otherwise, <statement>.

Sentence consumption rule (important):

• Each then, / but if ... then, / otherwise, branch consumes actions until the sentence ends.
• Separate multiple actions in a branch with commas.
• Use a period to end the full if sentence.
• A period before but if/otherwise is treated as part of the same if-chain when the chain continues.

If ready then, print "a", print "b", print "c".

Alternative keywords:

• When can replace If
• Else can replace Otherwise

While Loop#

While <condition>, <statements>.

Single-line example:

While the counter is less than 10, print the counter, increment the counter.

Multi-action loops are comma-separated actions within one sentence:

While x is less than 5, print x, increment x, print "looping".

Loops inside functions work naturally:

To sum of a number called n.
  a number called total is 0.
  a number called i is 1.
  While i is less than or equal to n, total is total add i, i is i add 1.
  Return a number, total.

For Each Loop#

Range-based:

For each number from <start> to <end>, <statement>.

Example:

For each number from 1 to 10, print the number.

Inside the loop:

• the number refers to the current iteration value

List-based:

For each <variable> in <list>, <statement>.

Example:

a list called nums is [1, 2, 3].
For each n in nums, print the n.

Repeat#

Run a body a fixed number of times.

Repeat <count> times, <statements>.

Single-line example:

Repeat 3 times, print "hello".

Multi-action loops are comma-separated actions within one sentence, exactly like While:

Repeat 2 times, print "a", print "b".

This prints a, b, a, b — two actions per iteration, two iterations.

Termination. Repeat closes by the same rules as While and For each: a period ends the body (and closes the construct — rule 1), and a blank line force-closes it (rule 2). The statements after a closing period belong to the surrounding scope, not the loop:

Repeat 2 times, print "r".
Print "after".

→ r r after

Because a period closes the construct, periods stack: write one period per level you want to close, so a Repeat nested in another loop takes two periods to close both (see Closing more than one level):

For each n from 1 to 2,
    Repeat 2 times, print "r"..
Print "after".

→ r r r r after

Loop Control#

Break.
Continue.

Program Termination#

Immediately exit the program with an exit code:

Exit <code>.

Examples:

Exit 0.                              (Success)
Exit 1.                              (General error)

If arguments's empty then,
    Print "Usage: ./program <file>".
    Exit 1.

Notes:

• Exit code defaults to 0 if not specified
• All resources are automatically cleaned up before exit
• Alternative keywords: quit, terminate

Increment/Decrement#

Increment the counter.
Decrement the value.