grammar SimpleDeclarative;

function 
	:	WORD COLON 'function' expression(ARROW expression)? setFuncBody SEMICOLON;

setFuncBody
	:	BRACESTART BRACEEND | BRACESTART expression ARROW expression (COMMA expression ARROW expression)* BRACEEND;
	;

	
set 	:	BRACESTART BRACEEND | '{' set_member (COMMA  set_member)* BRACEEND;
set_member:	(atom COLON)=> atom COLON expression (OR expression)* | (expression EQUAL)=> equation | expression;


expression
	:	(LET set)? (atom | set) (WHERE set)?;
	
equation	:	expression EQUAL expression;

atom	:	WORD | NUMBER;

WHERE	:	'where';
LET	:	'let';
EQUAL	:	'=';
SEMICOLON:	';';
OR	:	'|';
COLON	:	':';
ARROW	:	'->';
BRACESTART	: '{';	
BRACEEND	: '}';
COMMA	:	',';
NUMBER	: (DIGIT)+ ;
WORD	:	(LETTER)+;

fragment 
DIGIT	: '0'..'9' ;

fragment 
LETTER	: 'a'..'z';	

WHITESPACE : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ 	{ $channel = HIDDEN; } ;