247 lines
8.8 KiB
C++
247 lines
8.8 KiB
C++
/* file parser.hpp
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*
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* author: Roland Conybeare, Jul 2024
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*/
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#pragma once
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#include "exprstatestack.hpp"
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#include "envframestack.hpp"
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#include "parser_result.hpp"
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#include "parserstatemachine.hpp"
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#include <stdexcept>
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namespace xo {
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namespace scm {
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/** schematica parser
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*
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* Examples:
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*
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* decltype point
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*
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* // forward declarations
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* decl pi : f64;
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* decl fib(n : i32) -> i32;
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*
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* def pi = 3.14159265; // constant. = is single assignment
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*
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* def fib(n : i32) -> i32 {
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* // nested defs ok
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* def aux(n : i32, s1 : i32, s2 : i32) -> i32 {
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* // or:
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* // (n == 0) ? s1 : aux(n - 1, s1 + s2, s1)
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* //
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* if (n == 0) {
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* s1;
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* } else {
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* aux(n - 1, s1 + s2, s1);
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* }
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*
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* // or:
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* // if (n == 0) ? s1 : aux(n - 1, s1 + s2, s1)
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* }
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*
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* aux(n=n, s1=1, s2=0);
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* }
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*
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* def x := "fu"; // non-constant
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* x += "bar";
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*
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* def anotherfib = lambda(n : i32) { fib(n) };
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*
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* def any : object;
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* def l : list<object> = '();
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*
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* deftype point :: {x : f64, y : f64};
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* deftype polar :: {arg : f64, mag : f64};
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*
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* def polar2rect(pt : polar) -> point {
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* point(x = pt.mag * cos(arg),
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* y = pt.mag * sin(arg));
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* }
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*
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* Grammar:
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* toplevel-program = $toplevel-expression(1); ..; $toplevel-expression(n)
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*
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* if interactive:
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* toplevel-expression = expression
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* else
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* toplevel-expression = type-decl | define-expr
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*
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* type-decl = decltype $typename [<$tp1 .. $tpn>]
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* expression = type-decl
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* | define-expr
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* | literal-expr
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* | variable-expr
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* | apply-expr
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* | if-expr
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* | lambda-expr
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* | arithmetic-expr
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* | block
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*
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* define-expr = type-decl
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* | type-def
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* | variable-def
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* | function-decl
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* | function-def
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*
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* type-def = deftype $typename [<$tp1 .. $tpn>] :: type-def-rhs
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* type-def-rhs = object
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* | bool
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* | i128 | i64 | i32 | i16 | i8
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* | f128 | f64 | f32 | f16
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* | struct $typename { ($membername(i) : $typename(i))* }
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* [end $typename]
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* | tuple $typename { $typename(1), .., $typename(n) }
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* [end $typename]
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* | copytype $typename
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* | subtype $typename { ($member(i) : $typename(i))* }
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*
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* variable-def = decl $varname [: $typename] [= expression]
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* function-decl = decl $functionname($varname(1) : $typename(1),
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* ..,
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* $varname(n) : $typename(n)) -> $typename[ret]
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* function-def = def $functionname($varname(1) : $typename(1),
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* ..,
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* $varname(n) : $typename(n)) [-> $typename[ret]]
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* body-expr
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* [ end $functionname ]
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* literal-expr = boolean-literal
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* | integer-literal
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* | fp-literal
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* | string-literal
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* | symbol-literal
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* | struct-literal
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*
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*
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* boolean-literal = true | false
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*
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* variable-expr = $varname
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* apply-expr = fn-expr(arg-expr(1), .., arg-expr(n))
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* fn-expr = expression
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* arg-expr(i) = expression
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*
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* if-expr = if (test-expr) then-block else else-block
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* | ((test-expr) ? then-expr : else-expr)
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* test-expr = expression
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* then-block = block
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* else-block = block
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*
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* block = { (definition | expression)* }
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*
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* lambda-expr = lambda ($paramname(1) : $type(1),
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* ..,
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* $paramname(n) : $type(n)) body-expr
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* body-expr = expression
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*
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* arithmetic-expr = expression binop expression
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*
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* binop = +
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* | -
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* | *
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* | /
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* | |
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* | &
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* | ^
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* | ==
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* | !=
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* | <
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* | <=
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* | =>
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* | >
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*
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**/
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class parser {
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public:
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using Expression = xo::ast::Expression;
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using token_type = exprstate::token_type; // token<char>;
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public:
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/** create parser in initial state;
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* parser is ready to receive tokens via @ref include_token
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*
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* @p debug_flag true to enable debug logging
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**/
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explicit parser(bool debug_flag);
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/** true if parser is at top-level, i.e. ready for next top-level expression **/
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bool is_at_toplevel() const { return stack_size() == 0; }
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/** for diagnostics: number of entries in parser stack **/
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std::size_t stack_size() const { return psm_.xs_stack_.size(); }
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/** for diagnostics: exprstatetype at level @p i
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* (taken relative to top of stack)
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*
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* @pre 0 <= i < stack_size
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**/
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exprstatetype i_exstype(std::size_t i) const {
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std::size_t z = psm_.xs_stack_.size();
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if (i < z) {
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return psm_.xs_stack_[i]->exs_type();
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}
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/* out of bounds */
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return exprstatetype::invalid;
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}
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exprstate const * i_exstate(std::size_t i) const {
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std::size_t z = psm_.xs_stack_.size();
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if (i < z) {
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return psm_.xs_stack_[i].get();
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}
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/* out of bounds */
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return nullptr;
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}
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/** true iff parser contains state for an incomplete expression.
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* For this to be true, parser must have consumed at least one token
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* since end of last toplevel expression
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**/
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bool has_incomplete_expr() const;
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/** put parser into state for beginning an interactive session.
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**/
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void begin_interactive_session();
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/** put parser into state for beginning of a translation unit
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* (i.e. input stream)
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**/
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void begin_translation_unit();
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/** include next token @p tk and increment parser state.
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*
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* @param tk next input token
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* @return parsed expression, if @p tk completes an expression.
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* otherwise nullptr
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**/
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const parser_result & include_token(const token_type & tk);
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/** reset to starting parsing state.
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* use this after encountering an error, to avoid cascade of
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* spurious secondary errors.. particularly important when
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* invoked asa part of a REPL.
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**/
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void reset_to_idle_toplevel();
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/** print human-readable representation on stream @p os **/
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void print(std::ostream & os) const;
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private:
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/** state machine **/
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parserstatemachine psm_;
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}; /*parser*/
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inline std::ostream &
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operator<< (std::ostream & os,
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const parser & x) {
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x.print(os);
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return os;
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}
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} /*namespace scm*/
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} /*namespace xo*/
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/* end parser.hpp */
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