declarations.html

declarations.grm

// FILE. . . . . /home/hak/hlt/src/hlt/language/jaccapps/aql/sources/declarations.grm
// EDIT BY . . . Hassan Ait-Kaci
// ON MACHINE. . Hp-Dv7
// STARTED ON. . Wed Oct 17 23:32:58 2012

This is part of the AQL language grammar and contains its operator declarations. See AQL's predefined operators.

Author: Hassan Aït-Kaci

Copyright: © by the author

Version: Last modified on Wed Oct 17 23:49:45 2012 by hak



/* *** This contains the declaration part of grammar  **** */

/* ************************************************************************************* */
/* *******************************  START  OF  DECLARATIONS **************************** */
/* ************************************************************************************* */

%doc 'operator'

The first argument of $operator$ can be any syntactically well-formed AQL functor (an $Operator$). In particular, it need not be known as operator prior to runtime. AQL's tokenizer will recognize as a functor any token that is either an AQL identifier ($ID$), or a maximal sequence of non alphanumerical characters. AQL also supports the classical prefix function notation used in math and conventional programming. Thus, any AQL functor, whether declared operator or not, can always be parsed as a prefix operator preceding a parenthesized comma-separated sequence of arguments. Whether it is a declared operator determines how it may be parsed otherwise. For example:

          AQL> 1 + 2;
          3 : int
          AQL> +(1,2). 
          3 : int

Note that because AQL's functions are first-class citizens, defined functors are themselves expressions of higher-types and can also be parsed as $UntypedExpression$s (see $OperatorExpression$).

The second argument of $operator$ is an $INT$ and denotes the binding looseness (as opposed to precedence) of the given operator. AQL uses the same dynamic operator specification used by Prolog's op/3 meta-operator. Note that looseness works as the opposite of what is known as operator binding precedence used in parsing: the smaller an operator's binding looseness, the higher its precedence. In fact, if the looseness is L, then the precedence is P = 1200-L+1. Thus, both binding looseness and precedence range inclusively from 1 (min looseness, max precedence) to 1200 (max looseness, min precedence).

The third argument of $operator$ is called the operator's specifier. It is a symbol that encodes three kinds of information concerning the operator:

arity (unary or binary),
fixity (prefix, infix, or postfix),
associativity (left-, right-, or non-associative).

The specifier is an identifier consisting of either two or three of the letters 'f', 'x', and 'y', which are interpreted as follows. The letter 'f' stands for the operator's position in an expression, and the letters 'x' and 'y' stand for the arguments' positions. The letters 'f', 'y', and 'x', are simply mnemonics for, respectively, "functor" (i.e., indicating the position of the operator symbol with respect to its argument(s)), "yes" (i.e., the argument associates on this side of the operator), and "no" (i.e., the does not associate on this side of the operator). In other words, a 'y' occurring on the left (resp., right) of 'f', means that the operator is left-associative (resp., right-associative). An 'x' occurring on the left (resp., right) of 'f', means that the operator is not left-associative (resp., right-associative). Thus, the possible operator specifiers are:

Specifier Arity Fixity Associativity

fx unary prefix non-associative

fy unary prefix right-associative

xf unary postfix non-associative

yf unary postfix left-associative

xfx binary infix non-associative

xfy binary infix right-associative

yfx binary infix left-associative

Note that yfy is not allowed as an operator specifier because that would mean an ambiguous way of parsing the operator by associating either to the left or to the right.



/* ************************************************************************************* */

%import hlt.language.design.kernel.*;
%import hlt.language.design.kernel.Compiler;
%import hlt.language.design.types.*;
%import hlt.language.design.instructions.*;
%import hlt.language.design.backend.*;
%import hlt.language.design.backend.Runtime;

%import hlt.language.tools.Misc;
%import hlt.language.tools.Debug;
%import hlt.language.util.Stack;
%import hlt.language.util.Error;
%import hlt.language.util.Span;
%import hlt.language.util.Locatable;

%import hlt.language.io.CircularInclusionException;

%import java.util.HashMap;

%import java.io.PrintStream;
%import java.io.FileNotFoundException;

/* ************************************************************************ */

%start Statements_opt

%nodeprefix "AQL_"
%nodesuffix ""

%dynamic Operator
%Operator '||' xfy 800
%Operator '&&' xfy 700
%Operator '==' xfy 600
%Operator '!=' xfy 600
%Operator 'in' xfx 590
%Operator 'C=' yfx 590
%Operator 'U=' xfy 580
%Operator '=U' xfy 580
%Operator '-=' xfy 580
%Operator '^=' xfy 575
%Operator '=^' xfy 575
%Operator 'I=' xfy 570
%Operator '=I' xfy 570
%Operator 'U'  yfx 560
%Operator '^'  yfx 555
%Operator 'I'  yfx 550
%Operator '<'  xfx 500
%Operator '<=' xfx 500
%Operator '>'  xfx 500
%Operator '>=' xfx 500
%Operator '..' xfx 450
%Operator 'max' yfx 440
%Operator 'min' yfx 430
%Operator '+'  xfy 400
%Operator '-'  yfx 400
%Operator '*'  yfx 300
%Operator '/'  yfx 300
%Operator '%'  yfx 300
%Operator '**' yfx 200
%Operator '!'   fy 100
%Operator '-'   fy 100
%Operator '+'   fy 100
%Operator 'set' fx 100
%Operator 'bag' fx 100
%Operator 'list' fx 100
%Operator 'strip' fy 50

%left  29 '@'
%left  28 'as'
%token 27 INT REAL CHAR STRING ID SPECIFIER '<' '>'
%right 26 '->'
%left  25 '.'
%right 24 '$'
%token 23 '[' ']'
%token 22 '(' ')'


/* ************************************************************************************* */
/* *****************************    END  OF  DECLARATIONS    *************************** */
/* ************************************************************************************* */

This file was generated on Fri Oct 19 10:29:59 PDT 2012 from file declarations.grm
by the hlt.language.tools.Hilite Java tool written by Hassan Aït-Kaci