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parser.cpp
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parser.cpp
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#include "parser.hpp"
#include "syntax.hpp"
#include "lang/parsing.hpp"
#include "lang/debug.hpp"
#include <iostream>
// -------------------------------------------------------------------------- //
// Parsers
//
// The grammar of the term language is laid out like much like the
// that of C or C++. That is, there are several "extension points" in
// the grammar where a term may be added. These are:
//
// primary -- Parsed at the highest precedence
// postfix -- A left-associative binary operator
// prefix -- A unary expression whose operator precedes the operand
//
// Note that the same structure exists for the type parser.
Tree* parse_primary_expr(Parser&);
Tree* parse_postfix_expr(Parser&);
Tree* parse_prefix_expr(Parser&);
Tree* parse_expr(Parser&);
Tree* parse_name(Parser&);
// Parse a name.
//
// name ::= identifier
Tree*
parse_name(Parser& p) {
if (const Token* k = parse::accept(p, identifier_tok))
return new Id_tree(k);
return nullptr;
}
// Parse a unit literal.
//
// unit-lit ::= 'unit'
Tree*
parse_unit_lit(Parser& p) {
if (const Token* k = parse::accept(p, unit_tok))
return new Lit_tree(k);
return nullptr;
}
// Parse a boolean literal.
//
// boolean-lit ::= 'true' | 'false'
Tree*
parse_boolean_lit(Parser& p) {
if (const Token* k = parse::accept(p, true_tok))
return new Lit_tree(k);
if (const Token* k = parse::accept(p, false_tok))
return new Lit_tree(k);
return nullptr;
}
// Parse an integer literal.
//
// integer-literal ::= decimal-literal-token
//
// TODO: Allow for binary, octal, and hexadecimal integers.
Tree*
parse_integer_lit(Parser& p) {
if (const Token* k = parse::accept(p, decimal_literal_tok))
return new Lit_tree(k);
return nullptr;
}
// Parse a string literal.
//
// string-literal ::= string-literal-token
Tree*
parse_string_lit(Parser& p) {
if (const Token* k = parse::accept(p, string_literal_tok))
return new Lit_tree(k);
return nullptr;
}
// Parse a type literal.
//
// type-literal ::= 'Unit' | 'Bool' | 'Nat'
Tree*
parse_type_lit(Parser& p) {
if (const Token* k = parse::accept(p, unit_type_tok))
return new Lit_tree(k);
if (const Token* k = parse::accept(p, bool_type_tok))
return new Lit_tree(k);
if (const Token* k = parse::accept(p, nat_type_tok))
return new Lit_tree(k);
return nullptr;
}
// Parse a literal expression.
//
// literal-expr ::= unit-literal
// | boolean-literal
// | integer-literal
// | string-literal
// | type-literal
Tree*
parse_literal_expr(Parser& p) {
if (Tree* t = parse_unit_lit(p))
return t;
if (Tree* t = parse_boolean_lit(p))
return t;
if (Tree* t = parse_integer_lit(p))
return t;
if (Tree* t = parse_string_lit(p))
return t;
if (Tree* t = parse_type_lit(p))
return t;
return nullptr;
}
// Parse an identifer.
//
// id-expr ::= name
Tree*
parse_id_expr(Parser& p) { return parse_name(p); }
// Parse an inititializer.
//
// init-expr ::= identifier '=' expr
Tree*
parse_init_expr(Parser& p) {
if (Tree* n = parse_name(p))
if (parse::expect(p, equal_tok)) {
if (Tree* t = parse_expr(p))
return new Init_tree(n, t);
else
parse::parse_error(p) << "expected 'expr' after '='";
}
return nullptr;
}
// Parse a variable declaration in a lambda expression.
//
// parm-decl ::= identifier ':' expr
Tree*
parse_parm_decl(Parser& p) {
if (Tree* n = parse_name(p))
if (parse::expect(p, colon_tok)) {
if (Tree* t = parse_expr(p))
return new Var_tree(n, t);
else
parse::parse_error(p) << "expected 'expr' after ':'";
}
return nullptr;
}
// Parse a parameter list.
//
// parm-list ::= parm | parm-list ',' parm
Tree_seq*
parse_parm_list (Parser& p) {
Tree_seq* ts = new Tree_seq();
while (1) {
// Parse the next paramter.
if (Tree* t = parse_parm_decl(p)) {
ts->push_back(t);
} else {
parse::parse_error(p) << "expected 'parm'" ;
return nullptr;
}
// Check for the end of the list.
if (parse::next_token_is(p, rparen_tok))
break;
// Ensure that the next element is a comma.
if (not parse::expect(p, comma_tok))
return nullptr;
}
return ts;
}
// Parse a parameter clause.
//
// parm-list ::= '(' [parm-list]? ')'
Tree_seq*
parse_parm_clause(Parser& p) {
if (parse::accept(p, lparen_tok))
if (Tree_seq* ps = parse_parm_list(p))
if (parse::expect(p, rparen_tok))
return ps;
return nullptr;
}
// Parse a lambda abstraction.
//
// lambda-expr ::= '\' parm-decl ':' type '=>' term
// | '\' parm-list '=>' term
Tree*
parse_lambda_expr(Parser& p) {
if (const Token* k = parse::accept(p, backslash_tok)) {
if(Tree* v = parse_parm_decl(p)) {
if (parse::expect(p, map_tok)) {
if (Tree* t = parse_expr(p))
return new Abs_tree(k, v, t);
else
parse::parse_error(p) << "expected 'expr' after '.'";
}
} else if (Tree_seq* ps = parse_parm_clause(p)) {
if (parse::expect(p, map_tok)) {
if (Tree* t = parse_expr(p))
return new Fn_tree(k, ps, t);
else
parse::parse_error(p) << "expected 'expr' after '.'";
}
} else {
parse::parse_error(p) << "expected 'var-decl' or 'parm-clause' after '\\'";
}
}
return nullptr;
}
// Parse an element of a tuple or a variant.
//
// elem ::= var | init | expr
Tree*
parse_elem(Parser& p) {
if (parse::next_token_is(p, identifier_tok)) {
if (parse::nth_token_is(p, 1, colon_tok))
return parse_parm_decl(p);
if (parse::nth_token_is(p, 1, equal_tok))
return parse_init_expr(p);
parse::parse_error(p) << "expected ':' or '=' after 'identifier'";
return nullptr;
}
return parse_expr(p);
}
// Parse a comma separated sequence of elements in
// either a tuple or a variant.
//
// elem-list ::= elem | elem-list ',' elem
Tree_seq*
parse_elem_list(Parser& p, Token_kind close_tok) {
Tree_seq* ts = new Tree_seq();
while (true) {
// Try parsing the next element.
if (Tree* t = parse_elem(p))
ts->push_back(t);
else
return nullptr;
// Either break or continue.
if (parse::next_token_is(p, close_tok))
break;
if (parse::next_token_is(p, rbracket_tok))
break;
parse::expect(p, comma_tok);
}
return ts;
}
// Parse a comma-separated sequence of expressions that are by a
// enclosed by pair of tokens.
//
// enclosed-seq(open, close) ::= open [elem-seq]? close
//
// Here 'open' and 'close' are tokens represening the opening and
// closing tokens of the enclosed sequence. Note that the sequence
// may be empty.
template<typename T>
Tree*
parse_enclosed_seq(Parser& p, Token_kind open_tok, Token_kind close_tok) {
if (const Token* k = parse::accept(p, open_tok)) {
if (parse::accept (p, close_tok))
return new T(k, new Tree_seq());
if (Tree_seq* ts = parse_elem_list(p, close_tok)) {
if (parse::expect(p, close_tok))
return new T(k, ts);
} else {
// TODO: expected after the open_token
parse::parse_error(p) << "expected 'elem-list'";
}
}
return nullptr;
}
// Parse a tuple expression.
//
// tuple-expr ::= '{' t1, ..., tn '}'
//
// TODO: There is currently no way to distinguish between the type of
// the empty tuple and its value. There are at least two reasonable
// solutions: allow the empty tuple to be used in place of a type, or
// provide explicit syntax for differentiating the two.
Tree*
parse_tuple_expr(Parser& p) {
return parse_enclosed_seq<Tuple_tree>(p, lbrace_tok, rbrace_tok);
}
// Parse a list expression.
//
// list-expr ::= '[' t1, ..., tn ']'
Tree*
parse_list_expr(Parser& p) {
return parse_enclosed_seq<List_tree>(p, lbracket_tok, rbracket_tok);
}
// Parse a variant expression.
//
// tuple-expr ::= '<' t1, ..., tn '>'
Tree*
parse_variant_expr(Parser& p) {
parse_enclosed_seq<Variant_tree>(p, langle_tok, rangle_tok);
}
// Parse a grouped expression.
//
// grouped-expr ::= '(' [comma-expr]? ')'s
//
// Note the this is only a grouped expression when the form
// is '(e)' where 'e' is some expression. If the expression
// is of the form '()' or '(e1, ..., en)', then this is a comma
// epxression.
Tree*
parse_grouped_expr(Parser& p) {
if (const Token* k = parse::accept(p, lparen_tok)) {
// This is a comma expression.
if (parse::accept(p, rparen_tok))
return new Comma_tree(k, new Tree_seq());
if (Tree* t = parse_expr(p)) {
// This is a grouped subexpression.
if (parse::accept(p, rparen_tok)) {
return t;
}
// This is a grouped sub-expression.
Tree_seq* ts = new Tree_seq {t};
while (parse::accept(p, comma_tok)) {
if (Tree* t = parse_expr(p))
ts->push_back(t);
else
return nullptr;
}
// Make sure we have a closing rparen.
if (parse::expect(p, rparen_tok)) {
return new Comma_tree(k, ts);
}
} else {
parse::parse_error(p) << "expected 'expr' after '('";
}
}
return nullptr;
}
// Parse selection.
//
// stmt ::= select col from table where bool
Tree*
parse_select_expr(Parser& p) {
if(const Token* s = parse::accept(p, select_tok)) {
if (Tree* t1 = parse_expr(p)) {
if(parse::expect(p, from_tok)) {
if (Tree* t2 = parse_expr(p)) {
if(parse::expect(p, where_tok)) {
if (Tree* t3 = parse_expr(p)) {
return new Select_tree(s,t1,t2,t3);
}
}
}
}
}
}
return nullptr;
}
// Parse a primary expression.
//
// primary-term ::= primary-lambda-term | grouped-term
Tree*
parse_primary_expr(Parser& p) {
if (Tree* t = parse_literal_expr(p))
return t;
if (Tree* t = parse_lambda_expr(p))
return t;
if (Tree* t = parse_id_expr(p))
return t;
if (Tree* t = parse_tuple_expr(p))
return t;
if (Tree* t = parse_list_expr(p))
return t;
if (Tree* t = parse_variant_expr(p))
return t;
if (Tree* t = parse_grouped_expr(p))
return t;
return nullptr;
}
// Parse an application expr.
//
// application-expr ::= postfix-expr primary-expr
Tree*
parse_application_expr(Parser& p, Tree* t1) {
if (Tree* t2 = parse_primary_expr(p))
return new App_tree(t1, t2);
return nullptr;
}
// Parse a dot expression.
//
// dot-expr ::= postfix-expr '.' primary-expr
Tree*
parse_dot_expr(Parser& p, Tree* t1) {
if (parse::accept(p, dot_tok))
if (Tree* t2 = parse_primary_expr(p))
return new Dot_tree(t1, t2);
else
parse::parse_error(p) << "expected 'primary-expr' after '.'";
return nullptr;
}
// Parse an and expression
//
// and-expr ::= expr and expr
Tree*
parse_and_expr(Parser& p, Tree* t1) {
if(parse::accept(p, and_tok)) {
if(Tree* t2 = parse_expr(p))
return new And_tree(t1, t2);
else
parse::parse_error(p) << "expected 'expr' after 'and'";
}
return nullptr;
}
// Parse an or expression
//
// or-expr ::= expr or expr
Tree*
parse_or_expr(Parser& p, Tree* t1) {
if(parse::accept(p, or_tok)) {
if(Tree* t2 = parse_expr(p))
return new Or_tree(t1, t2);
else
parse::parse_error(p) << "expected 'expr' after 'or'";
}
return nullptr;
}
// Parse an eq-comp expression
//
// eq-comp-expr ::= expr == expr
Tree*
parse_eq_comp_expr(Parser& p, Tree* t1) {
if(const Token* t = parse::accept(p, eq_comp_tok)) {
if(Tree* t2 = parse_expr(p))
return new Eq_comp_tree(t1, t2);
else
parse::parse_error(p) << "expected 'expr' after '=='";
}
return nullptr;
}
// Parse an less expression
//
// less-expr ::= expr < expr
Tree*
parse_less_expr(Parser& p, Tree* t1) {
if(const Token* t = parse::accept(p, less_tok)) {
if(Tree* t2 = parse_expr(p))
return new Less_tree(t1, t2);
else
parse::parse_error(p) << "expected 'expr' after '<'";
}
return nullptr;
}
// Parse a union expression
//
// union-expr ::= expr union expr
Tree*
parse_union(Parser& p, Tree* t1) {
if(parse::accept(p, union_tok)) {
if(Tree* t2 = parse_expr(p))
return new Union_tree(t1, t2);
else
parse::parse_error(p) << "expected 'expr' after 'union'";
}
return nullptr;
}
// Parse an intersect expression
//
// intersect-expr ::= expr union expr
Tree*
parse_intersect(Parser& p, Tree* t1) {
if(parse::accept(p, intersect_tok)) {
if(Tree* t2 = parse_expr(p))
return new Intersect_tree(t1, t2);
else
parse::parse_error(p) << "expected 'expr' after 'intersect'";
}
}
// Parse an except expression
//
// except-expr ::= expr except expr
Tree*
parse_except(Parser& p, Tree* t1) {
if(parse::accept(p, except_tok)) {
if(Tree* t2 = parse_expr(p))
return new Except_tree(t1, t2);
else
parse::parse_error(p) << "expected 'table_expr' after 'Join'";
}
}
// Parse Join.
// stm t1 join t2
Tree*
parse_join(Parser& p, Tree* t1) {
if(const Token* s = parse::accept(p, join_tok)) {
if(Tree* t2 = parse_expr(p))
if(parse::expect(p, on_tok))
if(Tree* t3 = parse_expr(p))
return new Join_on_tree(s,t1,t2,t3);
else
parse::parse_error(p) << "expected 'expr' after 'on'";
else
parse::parse_error(p) << "expected 'expr' after 'join'";
else
parse::parse_error(p) << "expected 'expr' before 'join'";
}
return nullptr;
}
// Bind a term to a reference
// t as id
Tree*
parse_as(Parser& p, Tree* t1) {
if(const Token* t = parse::accept(p, as_tok)) {
if(Tree* t2 = parse_name(p)) {
return new As_tree(t1, t2);
}
else
parse::parse_error(p) << "expected 'id' after 'as'";
}
return nullptr;
}
// Parse a postfix expr.
//
// postfix-expr ::= applicaiton-expr
Tree*
parse_postfix_expr(Parser& p) {
if (Tree* t1 = parse_primary_expr(p)) {
while (t1) {
if (Tree* t2 = parse_dot_expr(p, t1))
t1 = t2;
else if (Tree* t2 = parse_application_expr(p, t1))
t1 = t2;
else if (Tree* t2 = parse_and_expr(p, t1))
t1 = t2;
else if (Tree* t2 = parse_or_expr(p, t1))
t1 = t2;
else if (Tree* t2 = parse_eq_comp_expr(p, t1))
t1 = t2;
else if (Tree* t2 = parse_less_expr(p, t1))
t1 = t2;
else if (Tree* t2 = parse_union(p, t1))
t1 = t2;
else if (Tree* t2 = parse_intersect(p, t1))
t1 = t2;
else if (Tree* t2 = parse_except(p, t1))
t1 = t2;
else if (Tree* t2 = parse_join(p, t1))
t1 = t2;
else if (Tree* t2 = parse_as(p, t1))
t1 = t2;
else
break;
}
return t1;
}
return parse_primary_expr(p);
}
// Parse an if-term.
//
// if-term ::= 'if' term 'then' term 'else' term
Tree*
parse_if_expr(Parser& p) {
if (const Token* k = parse::accept(p, if_tok))
if (Tree* t1 = parse_expr(p)) {
if (parse::expect(p, then_tok))
if (Tree* t2 = parse_expr(p)) {
if (parse::expect(p, else_tok)) {
if (Tree* t3 = parse_expr(p))
return new If_tree(k, t1, t2, t3);
else
parse::parse_error(p) << "expected 'expr' after 'else'";
}
} else {
parse::parse_error(p) << "expected 'expr' after 'then'";
}
} else {
parse::parse_error(p) << "expected 'expr' after 'if'";
}
return nullptr;
}
// Parse a successor expression.
//
// succ-expr ::= 'succ' prefix-expr
Tree*
parse_succ_expr(Parser& p) {
if (const Token* k = parse::accept(p, succ_tok)) {
if (Tree* t = parse_prefix_expr(p))
return new Succ_tree(k, t);
else
parse::parse_error(p) << "expected 'prefix-expr' after 'succ'";
}
return nullptr;
}
// Parse a predecessor expression.
//
// pred-expr ::= 'pred' prefix-expr
Tree*
parse_pred_expr(Parser& p) {
if (const Token* k = parse::accept(p, pred_tok)) {
if (Tree* t = parse_prefix_expr(p))
return new Pred_tree(k, t);
else
parse::parse_error(p) << "expected 'prefix-expr' after 'pred'";
}
return nullptr;
}
// Parse an is-zero expression.
//
// iszero-expr ::= 'iszero' prefix-expr
Tree*
parse_iszero_expr(Parser& p) {
if (const Token* k = parse::accept(p, iszero_tok)) {
if (Tree* t = parse_prefix_expr(p))
return new Iszero_tree(k, t);
else
parse::parse_error(p) << "expected 'prefix-expr' after 'iszero'";
}
return nullptr;
}
// Parse a print expression.
//
// print-expr ::= 'print' expr
Tree*
parse_print_expr(Parser& p) {
if (const Token* k = parse::accept(p, print_tok)) {
if (Tree* t = parse_expr(p))
return new Print_tree(k, t);
else
parse::parse_error(p) << "expected 'expr' after 'print'";
}
return nullptr;
}
// Parse a typeof expression.
//
// typeof-expr ::= 'typeof' expr
Tree*
parse_typeof_expr(Parser& p) {
if (const Token* k = parse::accept(p, typeof_tok)) {
if (Tree* t = parse_expr(p))
return new Typeof_tree(k, t);
else
parse::parse_error(p) << "expected 'expr' after 'typeof'";
}
return nullptr;
}
// Parse a not expression
//
// not-expr ::= 'not' expr
Tree*
parse_not_expr(Parser& p) {
if (const Token* k = parse::accept(p, not_tok)) {
if (Tree* t = parse_expr(p))
return new Not_tree(k, t);
else
parse::parse_error(p) << "expected 'expr' after 'not'";
}
return nullptr;
}
// Parse the schema of a table
//
// schema-expr ::= [x1:T1,...,xn:Tn]
Tree_seq*
parse_schema_expr(Parser& p) {
if(parse::accept(p, lbracket_tok)) {
if(Tree_seq* schema = parse_elem_list(p, rbracket_tok)) {
if(parse::accept(p, rbracket_tok))
return schema;
else
parse::parse_error(p) << "Expected ']' after schema definition";
}
}
else
parse::parse_error(p) << "Expected '[' after 'table'";
return nullptr;
}
// Parse a prefix expr.
//
// prefix-expr ::= if-expr | succ-epxr | pred-expr | iszero-expr
// | not-expr | print-expr | typeof-expr
Tree*
parse_prefix_expr(Parser& p) {
if (Tree* t = parse_if_expr(p))
return t;
if (Tree* t = parse_select_expr(p))
return t;
if (Tree* t = parse_succ_expr(p))
return t;
if (Tree* t = parse_pred_expr(p))
return t;
if (Tree* t = parse_iszero_expr(p))
return t;
if (Tree* t = parse_print_expr(p))
return t;
if (Tree* t = parse_typeof_expr(p))
return t;
if (Tree* t = parse_not_expr(p))
return t;
return parse_postfix_expr(p);
}
// Parse an arrow expression.
//
// imp-expr ::= prefix-expr
// | prefix-expr '->' imp-expr
Tree*
parse_arrow_expr(Parser& p) {
if (Tree* l = parse_prefix_expr(p)) {
if (parse::accept(p, arrow_tok))
if (Tree* r = parse_arrow_expr(p))
return new Arrow_tree(l, r);
return l;
}
return nullptr;
}
// Parse an expression
//
// expr ::= prefix-expr
Tree*
parse_expr(Parser& p) {
return parse_arrow_expr(p);
}
// Parse an intializer clause
// initializer-clause:= '=' expr
Tree*
parse_required_initializer_clause(Parser& p) {
if (parse::accept(p, equal_tok))
if (Tree* t = parse_expr(p))
return t;
else
parse::parse_error(p) << "expected 'expr' after '='";
return nullptr;
}
// Parse a return type. This specifies the result type of a
// function declarator.
//
// return-type ::= '->' expr
Tree*
parse_return_type(Parser& p) {
if (parse::expect(p, arrow_tok))
if (Tree* t = parse_type_lit(p))
return t;
return nullptr;
}
// Parse a function declarator.
// fn-decl ::= n(p1, p2, ...) -> t
Tree*
parse_fn_decl(Parser& p, Tree* n) {
if (Tree_seq* ps = parse_parm_clause(p))
//parsing parameter list as Lambda abstraction \(pi:Ti).e
if (Tree* t = parse_return_type(p))
return new Func_tree(n, ps, t);
return nullptr;
}
// Parse a definition expression.
//
// def_const-expr ::= name '=' expr
Tree*
parse_const_decl(Parser& p,Tree *n,const Token *k) {
if (parse::accept(p, equal_tok)) {
if (Tree* e = parse_expr(p))
return new Def_tree(k, n, e);
else
parse::parse_error(p) << "expected 'expr' after '='";
}
return nullptr;
}
// Parse a def-decl.
//
// def-decl ::= const-decl | fn-decl
//
Tree*
parse_def_decl(Parser& p) {
if (const Token* k = parse::accept(p, def_tok))
if (Tree* n = parse_name(p)) {
// Parse the declarator.
Tree*d1=nullptr;
if (Tree* d2 = parse_const_decl(p, n,k))
d1=d2;
else if (Tree* d2 = parse_fn_decl(p, n))
d1=d2;
if (not d1) {
parse::parse_error(p) << "expected 'parameter-clause' after 'name'";
return nullptr;
}
// Parse the initializer.
if (Tree* e = parse_required_initializer_clause(p))
return new Def_tree(k, d1, e);
else
return d1;
}
else
return nullptr;
}
// Parse a statement.
//
// stmt ::= def-stmt | expr-stmt
Tree*
parse_stmt(Parser& p) {
if (Tree* t = parse_def_decl(p))
return t;
if (Tree* t = parse_expr(p))
return t;
return nullptr;
}
// Parse a program.
//
// program ::= stmt-list
// stmt-list ::= stmt ';' | stmt-list ';' stmt
//
Tree*
parse_program(Parser& p) {
Tree_seq* stmts = new Tree_seq();
while (not parse::end_of_stream(p)) {
// Parse the next statement...
if (Tree* s = parse_stmt(p))
stmts->push_back(s);
else
return nullptr;
// ... and it's trailing ';'
if (not parse::expect(p, semicolon_tok))
return nullptr;
}
return new Prog_tree(stmts);
}
// -------------------------------------------------------------------------- //
// Parser
// Parse a range of tokens.
Tree*
Parser::operator()(Token_iterator f, Token_iterator l) {
if (f == l)
return nullptr;
first = f;
last = l;
current = first;
use_diagnostics(diags);
return parse_program(*this);
}