Aladino syntax

The syntax of Aladino is quite simple. Here's the BNF grammar representation:

prog := stat_list

stat := expr

expr := expr BINOP expr
      | UNARYOP expr
      | TIMESTAMP
      | RELATIVE_TIMESTAMP
      | NUMBER
      | STRING
      | BOOLEAN
      | '(' expr ')'
      | '[' expr_list ']'
      | '$' IDENTIFIER '(' expr_list ')'
      | '(' expr_list '=>' expr  ')'

expr_list :=
        expr ',' expr_list
      | expr
      |

TIMESTAMP :=
        YYYYMMDD
      | YYYY-MM-DD
      | YYYYMMDDTHH:MM:SS
      | YYYY-MM-DDTHH:MM:SS

RELATIVE_TIMESTAMP := NUMBER TIME_UNIT ago

TIME_UNIT :=
        'year'   | 'years'
      | 'month'  | 'months'
      | 'week'   | 'weeks'
      | 'day'    | 'days'
      | 'hour'   | 'hours'
      | 'minute' | 'minutes'

BINOP :=
        '==' | '>=' | '>' | '<' | '<='
      | '&&' | '||'

UNARYOP := '!'

This allows us to specify:

1. Logical expressions: e.g. "a" == "a" or $fun() == 1;
2. Function calls: e.g. $label("bug")
3. Lambda functions: e.g. ($dev => $dev == $author())