Skip to main content

Control Flow

Conditional Statements​

Conditional statements are declared as if {condition} {...} else if {condition} {...} else {...}. Conditional statements can be nested.

    let a: u8 = 1u8;
    
    if a == 1u8 {
        a += 1u8;
    } else if a == 2u8 {
        a += 2u8;
    } else {
        a += 3u8;
    }

Leo also supports ternary expressions. Ternary expressions are declared as {condition} ? {then} : {else}, and can be nested.

let a: u8 = 1u8;    
a = (a == 1u8) ? a + 1u8 : ((a == 2u8) ? a + 2u8 : a + 3u8);

For Loops​

For loops are declared as for {variable: type} in {lower bound}..{upper bound}. The loop bounds must be integer constants of the same type. Furthermore, if the lower bound is superior or equal to the upper bound, the loop will result in no operations. Nested loops are supported.

  let count: u32 = 0u32;

  for i: u32 in 0u32..5u32 {
    count += 1u32;
  }

  return count; // returns 5u32

Return Statements​

Return statements are declared as return {expression};.

    let a: u8 = 1u8;
    
    if a == 1u8 {
        return a + 1u8;
    } else if a == 2u8 {
        return a + 2u8;
    } else {
        return a + 3u8;
    }