454 lines
15 KiB
C++
454 lines
15 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 "xo/expression/Expression.hpp"
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#include "xo/tokenizer/token.hpp"
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#include <stack>
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#include <stdexcept>
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namespace xo {
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namespace scm {
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// ----- exprir -----
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enum class exprirtype {
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invalid = -1,
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empty,
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symbol,
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expression,
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n_exprirtype
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};
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extern const char *
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exprirtype_descr(exprirtype x);
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inline std::ostream &
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operator<< (std::ostream & os,
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exprirtype x)
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{
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os << exprirtype_descr(x);
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return os;
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}
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/** intermediate representation for some part of an expression
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*
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* Examples:
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* 1. a variable name (but without type information)
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**/
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class exprir {
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public:
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using Expression = xo::ast::Expression;
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public:
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exprir() = default;
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exprir(exprirtype xir_type,
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const std::string & x)
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: xir_type_{xir_type}, symbol_name_{x} {}
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exprir(exprirtype xir_type,
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rp<Expression> expr)
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: xir_type_{xir_type}, expr_{std::move(expr)} {}
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exprirtype xir_type() const { return xir_type_; }
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const std::string & symbol_name() const { return symbol_name_; }
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const rp<Expression> & expr() const { return expr_; }
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void print(std::ostream & os) const;
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private:
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/** IR type code **/
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exprirtype xir_type_ = exprirtype::invalid;
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/** xir_type=symbol: a symbol (type or variable) name **/
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std::string symbol_name_;
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/** xir_type=expression: a completed expression **/
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rp<Expression> expr_;
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};
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inline std::ostream &
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operator<< (std::ostream & os, const exprir & x) {
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x.print(os);
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return os;
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}
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enum class exprstatetype {
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invalid = -1,
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/** toplevel of some translation unit **/
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expect_toplevel_expression_sequence,
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def_0,
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def_1,
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def_2,
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def_3,
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def_4,
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expect_rhs_expression,
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expect_symbol,
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n_exprstatetype
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};
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extern const char *
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exprstatetype_descr(exprstatetype x);
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inline std::ostream &
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operator<< (std::ostream & os, exprstatetype x) {
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os << exprstatetype_descr(x);
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return os;
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}
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enum class expractiontype {
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invalid = -1,
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push1,
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push2,
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keep,
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emit,
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pop,
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n_expractiontype
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};
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extern const char *
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expractiontype_descr(expractiontype x);
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inline std::ostream &
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operator<< (std::ostream & os, expractiontype x) {
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os << expractiontype_descr(x);
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return os;
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}
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/** an action associated with parser response to an incoming lexical
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**/
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class expraction {
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public:
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expraction() = default;
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expraction(expractiontype action_type,
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const exprir & expr_ir,
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exprstatetype push_exs1,
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exprstatetype push_exs2)
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: action_type_{action_type}, expr_ir_{expr_ir},
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push_exs1_{push_exs1}, push_exs2_{push_exs2}
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{}
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static expraction keep();
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static expraction emit(const exprir & ir);
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static expraction push2(exprstatetype s1, exprstatetype s2);
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expractiontype action_type() const { return action_type_; }
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const exprir & expr_ir() const { return expr_ir_; }
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exprstatetype push_exs1() const { return push_exs1_; }
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exprstatetype push_exs2() const { return push_exs2_; }
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void print(std::ostream & os) const;
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private:
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/**
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* push1: push new exprstate built from push_exs1_
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* push2: push new exprstate built from push_exs1_,
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* followed by push_exs2_
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* keep: keep current exprstate (which will have updated inplace)
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* pop: drop exprstate, report exprir to parent
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**/
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expractiontype action_type_ = expractiontype::invalid;
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/**
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* intermediate representation (pass to enclosing stack state)
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**/
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exprir expr_ir_;
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/** with action_type push1 or push2,
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* parser will push exprstate with this type
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**/
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exprstatetype push_exs1_ = exprstatetype::invalid;
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/** with action_type push2,
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* parser will push exprstate with this type
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* (after pushing exprstate built from push_exs1_)
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**/
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exprstatetype push_exs2_ = exprstatetype::invalid;
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};
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inline std::ostream &
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operator<< (std::ostream & os,
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const expraction & x)
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{
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x.print(os);
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return os;
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}
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/** state associated with a partially-parsed expression.
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**/
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class exprstate {
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public:
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using exprtype = xo::ast::exprtype;
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using token_type = token<char>;
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public:
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exprstate() = default;
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exprstate(exprstatetype exs_type) : exs_type_{exs_type} {}
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static exprstate expect_toplevel_expression_sequence() {
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return exprstate(exprstatetype::expect_toplevel_expression_sequence);
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}
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static exprstate def_0() {
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return exprstate(exprstatetype::def_0);
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}
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static exprstate expect_symbol() {
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return exprstate(exprstatetype::expect_symbol);
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}
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exprstatetype exs_type() const { return exs_type_; }
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/** true iff this parsing state admits a 'def' keyword
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* as next token
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**/
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bool admits_definition() const;
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/** true iff this parsing state admits a symbol as next token **/
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bool admits_symbol() const;
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/** true iff this parsing state admits a colon as next token **/
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bool admits_colon() const;
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/** true iff this parsing state admits a singleassign '=' as next token **/
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bool admits_singleassign() const;
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/** true iff this parsing state admits a 64-bit floating point literal token **/
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bool admits_f64() const;
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/** update exprstate in response to incoming token @p tk,
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* forward instructions to parent parser
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**/
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expraction on_input(const token_type & tk);
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/** update exprstate in response to IR (intermediate representation)
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* from nested parsing task
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**/
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expraction on_exprir(const exprir & ir);
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/** print human-readable representation on @p os **/
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void print(std::ostream & os) const;
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private:
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expraction on_def();
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expraction on_symbol(const token_type & tk);
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expraction on_colon();
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expraction on_singleassign();
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expraction on_f64(const token_type & tk);
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private:
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/**
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* def foo : f64 = 1
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* ^ ^ ^ ^ ^ ^ ^
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* | | | | | | (done)
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* | | | | | def_4:expect_rhs_expression
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* | | | | def_3
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* | | | def_2:expect_symbol
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* | | def_1
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* | def_0:expect_symbol
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* expect_toplevel_expression_sequence
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*
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* def_0:expect_symbol: got 'def' keyword, symbol to follow
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* def_1: got symbol name
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* def_2:expect_symbol got (optional) colon, type name to follow
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* def_3: got symbol type
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* def_4:expect_rhs_expression got (optional) equal sign, value to follow
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* (done): definition complete, pop exprstate from stack
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*
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**/
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exprstatetype exs_type_;
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/** e.g. foo in
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* def foo : f64 = 1
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**/
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std::string def_lhs_symbol_;
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/** e.g. f64 in
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* def foo : f64 = 1
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**/
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std::string def_lhs_type_;
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}; /*exprstate*/
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inline std::ostream &
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operator<< (std::ostream & os, const exprstate & x) {
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x.print(os);
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return os;
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}
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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 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 = expression*
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* type-decl = decltype $typename [<$tp1 .. $tpn>]
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* expression = 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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* | 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 = 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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* 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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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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parser() = default;
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/** for diagnostics: number of entries in parser stack **/
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std::size_t stack_size() const { return 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 = stack_.size();
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if (i < z) {
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return stack_[(z - 1) - 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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/** 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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rp<Expression> include_token(const token_type & tk);
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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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exprstate & top_exprstate();
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void push_exprstate(const exprstate & exs);
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void pop_exprstate();
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private:
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/** state recording state associated with enclosing expressions.
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*
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* Note: at least asof c++23, the std::stack api doesn't support access
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* to members other than the top.
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*
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* for stack with N elements (N = stack_.size()):
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* - bottom of stack is stack_[0]
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* - top of stack is stack_[N-1]
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**/
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std::vector<exprstate> stack_;
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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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