Control Flow

This topic documents control flow structures in the language.

Simple if Statement

The simple if statement checks the top element on the stack. If this value (<CONDITION>) is truthy (non-zero), the interpreter executes the block inside (<CODE>).

Syntax:

<CONDITION> if
  <CODE>
end

Example:

1 if
  10 Print
end
0 if
  20 Print
end

In this example, only 10 will be printed, as 1 is truthy and 0 is falsy.

Compound if Statement

The compound if statement checks the top element on the stack. If this value (<CONDITION>) is truthy, the interpreter executes the block inside (<CODE>). Otherwise, the interpreter executes the block after else (<OTHERWISE>).

Syntax:

<CONDITION> if
  <CODE>
else
  <OTHERWISE>
end

Example:

0 if
  10 Print
else
  20 Print
end

In this example, "20" will be printed because the condition is 0 (falsy).

Loops (loop)

The loop keyword creates an infinite loop.

Use break to exit the loop.

Use continue to jump to the next iteration.

Syntax:

loop
  <CODE>
end

Example with if and break:

0 loop
  dup Print
  dup 10 = if
    break
  end
  1 +
end

This will print 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 and then exit the loop.

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