// Convert an integer to a string
function itos : (int i) -> string 

// Convert a string to an integer.
// Return err if the string could not be parsed.
function stoi : (string s, int err) -> int

// Convert an integer i to a string containing the single character 
// whose ASCII code is i.
function itoc : (int i) -> string

// Convert an array of integers containing ASCII codes to a string
function atos : (array[int] a) -> string

// Convert a string to an array of integers containing ASCII codes 
function stoa : (string s)-> array[int]