Lexical Structure

Comments

^Lexer
LINE_COMMENT :
// (~\n)^*

BLOCK_COMMENT :
/* (BLOCK_COMMENT | ~*/)^* */

Comments have no effect on the program.

// This is a line comment

/*
 * And this is a multiline (block) comment.
 * The stars on the left are purely for aesthetics
 */

^Lexer
ID :
      (ID_START ID_CONT^*)_{Expect keywords}

ID_START :
      [a-z A-Z]

ID_CONT :
      [_ a-z A-Z 0-9]

^Syntax
ID_List :
ID (, ID)^* ,^?

Some valid identifiers are:

Some invalid identifiers are:

Keyword	Usage
`type`	Define a type, Existentials, Universals
`dec`	Declare a value
`def`	Define a value
`chan`	Channel expressions, Dualize types
`let`	Let expressions and statements
`do`	Do expressions
`in`	Let expressions, Do expressions
`begin`, `loop`	Iterative constructions, Recursive destruction (expression or statement)
`either`	Either types
`recursive`	Recursive types
`iterative`	Iterative types
`self`	Recursive and iterative types
`unfounded`	Escape totality checker in recursive expressions and statements

Symbol	Usage
`=`	Definitions (values and types), Let expressions and statements
`:`	Type annotations, Value declarations, Loop labels
`,`	Various enumerations
`!`	Unit type, expression, pattern, Break command
`?`	Bottom type, Continue command
`.`	Labels of either or choice types, used in various places
`<>`	Link commands
`<`	Type parameters and arguments
`>`	Type parameters and arguments
`=>`	Choice types and constructions, Match expressions and commands
`(` … `)`	Pairs, function application
`[` … `]`	Functions, pair destruction
`{` … `}`	Either and choice types, processes

Whitespace in Par serves merely the purpose of separating tokens. Whitespace characters are: