6. Control Flow

Control flow operations use brackets or parentheses to enclose evaluation scopes and execution bodies.

Conditionals (If & Else)

Syntax: ( cond statement1 statement2 ... ) -> ( elsestatement1 ... )

Examples

# If condition evaluates to true, execute the first block. 
# The second block (else) is optional.
(== age 18
    > "Welcome to adulthood!"
) -> (
    > "You are not 18."
)

# If blocks can be evaluated inline as well.
# The result is the last evaluated expression.
= a 2
= b 1
> (<< a b "A is less than B") -> ("A is not less than B")

Loops (While & For)

Syntax (While): [ cond statement1 statement2 ... ] Syntax (For): [ \ array iterator_name statement1 … ]`

Like conditionals, loop blocks can be evaluated inline. The value of a loop expression is determined by the last evaluated expression inside its body on its final iteration. If the loop condition is initially false (or the array is empty), the block returns 0.

You can break out of loop using <<< and continue the loop to the next iteration >>>. These do not change the returned result, it will still be the last evaluated expression.

Examples

# While Loop example
= i 0
[<< i 5
    > i
    = i + i 1
]

# For Loop iterating over an array
= my_arr <"A" "B" "C">
[`my_arr letter
    > letter
]

### Inline Evaluation Examples
# Loops can capture values inline. The result assigned is the last statement executed
# before the loop condition terminates or the loop finishes.

= counter 1
= total_sum 0

# The value assigned to 'result' will be the final value of 'total_sum' 
# evaluated right before the loop terminates.
= result [<< counter 4
    = total_sum + total_sum counter
    = counter + counter 1
    total_sum
]

> result   # Outputs: 6 (1 + 2 + 3)

# Inline For Loop capturing transformations
= numbers <10 20 30>
= running_total 0

# Iterates through the collection, altering an outside variable, and tracking 
# the final calculation state.
= final_value [`numbers num
    = running_total + running_total num
    * running_total 2
]

> final_value   # Outputs: 120 (The last calculation: (10 + 20 + 30) * 2 )

# Empty or Unexecuted loops return a default boundary value of 0
= unexecuted [<< 1 0
    "This will never run"
]
> unexecuted   # Outputs: 0