Loops (For, While)

Dflat provides a clean, modern syntax for iteration, supporting conditional while loops, range-based for loops, and collection iterators.

While Loops

Dflat supports both condition-first and body-first (do-while) loop structures.

• Standard While: Evaluates the condition before executing the block.

  while i < n { 
    Print(i)
  }
  

• Body-First While: Executes the block first, then evaluates the condition to determine if it should repeat.

  { 
     a--
  } while a > 0
  

In both cases, the condition does not require parentheses and must be castable to a boolean.

For Loops

The for loop in Dflat relies on ranges and iterators rather than traditional C-style iteration blocks. The loop variable always requires a type (explicitly stated or inferred via var). An untyped loop variable (e.g., for x in ...) results in a compile error.

• Exclusive Ranges (..): Iterates up to, but not including, the final value.

  for u8 i = 0..10 { }
  

• Inclusive Ranges (..=): Iterates up to and including the final value. Step increments can be appended using the step keyword.

  for u16 i = 0..=100 step i += 2 { }
  

• Decreasing Ranges: Counts down automatically when the start value is greater than the end value.

  for u8 i = 10..=1 { }
  

• Collection Iteration (in): Directly iterates over strings, lists, maps (with support for keys, values, or tuple destructuring), and ranges as virtual collections.

  for char c in "text" { }
  for u64 k in list.keys { }
  for string message in messages { }
  for (string key, i32 value) in map { }
  for var (key, value) in map { }
  

Loop Control & Labels

Dflat provides precise control over loop execution using standard keywords and label targeting.

• Continue: Skips the rest of the current iteration and proceeds to the next. Takes no labels.
• Break: Exits the innermost loop immediately. It can optionally target a specific label to break out of nested loops (e.g., break #Found#).
• Jump: Explicitly jumps to a defined label (e.g., jump #retry#). Jumps are strictly limited to the same block or an outer block; jumping into an inner block is prohibited.
• Validation: Using break or continue outside of a loop results in a compile error.

for i32 i = 0..max {
  for i32 x = 0..w {
    for i32 y = 0..h {
      if y > x then break
      if i == y * x then jump #outside#
    }
  }
#outside#
}

Labels are defined by wrapping a name in hashtags (e.g., #name#), must start and end with #, have no spaces, and contain at least one letter (allowed characters include letters, digits, and _ - + ! ? $ %).