Lists

There are two types of lists: tuples and lists.

Tuple is an immutable list of values. It is created with parenthesis enclosing a list of expressions. To create a tuple with one element, there must be an extra comma after the single expression. A tuple with no elements is an empty parenthesis. A tuple yields a value of type anvil.lang.tuple.

  tuple-expr := "(" ")" 
  tuple-expr := "(" expr "," ")" 
  tuple-expr := "(" expr-list [","] ")" 

List is a mutable list of values. It is created with curly braces enclosing a list of expressions. In order to prevent ambiguity with block statements, a backlash is inserted before the opening brace. List yields a value of type anvil.lang.list.

Lists can also be created using list compreshension, which will create a new list containing all the elements the yielded by the innermost expression inside comprehension.

  list-expr := "\{" expr-list [","] "}" 
  list-ctor := "\{" comprehension-foreach  "}" 
  comprehension-foreach :=  "foreach" "(" ... ")" comprehension 
  comprehension-if ::= "if" "(" expr ")" comprehension 
  comprehension := comprehension-foreach | comprehension-if | expr 

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