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xo-reader2: DApplySsm for apply expressions [WIP]

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Roland Conybeare 2026-02-11 16:02:41 -05:00
commit 40e1fb531d
7 changed files with 402 additions and 6 deletions
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165
include/xo/reader2/DApplySsm.hpp Normal file
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@ -0,0 +1,165 @@
/** @file DApplySsm.hpp
*
* @author Roland Conybeare, Feb 2026
**/
#pragma once
#include "DSyntaxStateMachine.hpp"
#include "syntaxstatetype.hpp"
#include <xo/expression2/ApplyExpr.hpp>
//#include <xo/facet/obj.hpp>
#include <string_view>
namespace xo {
namespace scm {
/**
* fn ( arg1 , arg2 , .. , argn )
* ^ ^ ^ ^ ^ ^ ^ ^ ^
* | | | | | | | | (done)
* | | | | | | | apply_3
* | | | | | | apply_2:expect_rhs_expression
* | | | | | apply_3
* | | | | apply_2:expect_rhs_expression
* | | | apply_3
* | | apply_2:expect_rhs_expression
* | apply_1
* apply_0:expect_rhs_expression
*
* apply_0 --on_expr()--> apply_1
* apply_1 --on_leftparen()--> apply_2
* apply_2 --on_expr()--> apply_3
* apply_3 --on_comma()--> apply_2
* --on_rightparen()-> (done)
*
* apply_0: start
* apply_1: leftparen following expr allows parser to recognize apply
* apply_2: expect next argument
* apply_3: got argument, expect comma or rightparen to continue
* (done): apply complete, pop exprstate from stack
*
* In practice will start in state apply_1
**/
enum class applyexprstatetype {
invalid = -1,
apply_0,
apply_1,
apply_2,
apply_3,
N
};
extern const char * applyexprstatetype_descr(applyexprstatetype x);
std::ostream &
operator<<(std::ostream & os, applyexprstatetype x);
/** @class DApplySsm
* @brief state machine for parsing a schematika function-call-expression
**/
class DApplySsm : public DSyntaxStateMachine<DApplySsm> {
public:
using Super = DSyntaxStateMachine<DApplySsm>;
using TypeDescr = xo::reflect::TypeDescr;
using AAllocator = xo::mm::AAllocator;
using DArena = xo::mm::DArena;
using ppindentinfo = xo::print::ppindentinfo;
//using Apply = xo::scm::Apply;
public:
/** @defgroup scm-applyssm-ctors constructors **/
///@{
/** construct apply ssm with @p fn_expr
* supplying function to be invoked.
*
* Expect during parsing of input like f(...)
* that we parse f before parser knows that it will be
* followed by leftparen
**/
explicit DApplySsm(obj<AExpression> fn_expr);
/** create instance using memory from @p parser_mm.
* with function to be called supplied by @p fn_expr.
**/
static DApplySsm * make(DArena & parser_mm,
obj<AExpression> fn_expr);
#ifdef NOT_YET
/**
* Start apply. Will trigger this after input like
* "fn("
*
* apply_xs remains on expr stack until closing right paren
* fn(arg1-expr, arg2-expr, ...)
*
* @p fnex expression in function position
* @p p_psm parser state machine
**/
static void start(rp<Expression> fnex,
parserstatemachine * p_psm);
#endif
///@}
/** @defgroup scm-applyssm-access methods **/
///@{
/** identify this nested state machine **/
static const char * ssm_classname() { return "DApplySsm"; }
/** current internal state **/
applyexprstatetype applystate() const noexcept { return applystate_; }
///@}
/** @defgroup ssm-applyssm-facet syntaxstatemachine facet methods **/
///@{
/** identifies the ssm implemented here **/
syntaxstatetype ssm_type() const noexcept;
/** mnemonic for expected remaining syntax for current parsing state **/
std::string_view get_expect_str() const noexcept;
#ifdef NOT_YET
virtual void on_expr(bp<Expression> expr,
parserstatemachine * p_psm) override;
virtual void on_comma_token(const token_type & tk,
parserstatemachine * p_psm) override;
virtual void on_leftparen_token(const token_type & tk,
parserstatemachine * p_psm) override;
virtual void on_rightparen_token(const token_type & tk,
parserstatemachine * p_psm) override;
virtual void print(std::ostream & os) const override;
virtual bool pretty_print(const print::ppindentinfo & ppii) const final override;
private:
static std::unique_ptr<apply_xs> make();
#endif
private:
/** current state of parser for this apply expression **/
applyexprstatetype applystate_ = applyexprstatetype::apply_0;
/** evaluates to function to be invoked **/
obj<AExpression> fn_expr_;
#ifdef NOT_YET
/** evaluates to the arguments to pass to @ref fn_ **/
std::vector<rp<Expression>> args_expr_v_;
#endif
};
} /*namespace scm */
namespace print {
#ifndef ppdetail_atomic
PPDETAIL_ATOMIC(xo::scm::applyexprstatetype);
#endif
}
} /*namespace xo*/
/* end DApplySsm.hpp */

4
include/xo/reader2/DDefineSsm.hpp
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@ -78,7 +78,7 @@ namespace xo {
using ppindentinfo = xo::print::ppindentinfo;
public:
/** @defgroup scm-define-ssm-facet constructors **/
/** @defgroup scm-definessm-ctors constructors **/
///@{
/** constructor; using @p def_expr for initial expression scaffold **/
@ -110,7 +110,7 @@ namespace xo {
defexprstatetype defstate() const noexcept { return defstate_; }
///@}
/** @defgroup scm-define-ssm-facet syntaxstatemachine facet methods **/
/** @defgroup scm-definessm-facet syntaxstatemachine facet methods **/
///@{
/** identifies the ssm implemented here **/

5
include/xo/reader2/syntaxstatetype.hpp
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@ -27,9 +27,12 @@ namespace xo {
/** handle ifelse-expression. See @ref DIfElseSsm **/
ifelseexpr,
/** handle sequence-expression. See @ref DSequenceSsm **/
/** handle sequence-expression syntax. See @ref DSequenceSsm **/
sequence,
/** handle apply-expression syntax. See @ref DApplySsm **/
apply,
/** rhs expression. state exists to achieve 1-token lookahead **/
progress,

4
src/reader2/CMakeLists.txt
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@ -37,6 +37,10 @@ set(SELF_SRCS
ISyntaxStateMachine_DLambdaSsm.cpp
IPrintable_DLambdaSsm.cpp
DApplySsm.cpp
# ISyntaxStateMachine_DApplySsm.cpp
# IPrintable_DApplySsm.cpp
DParenSsm.cpp
ISyntaxStateMachine_DParenSsm.cpp
IPrintable_DParenSsm.cpp

221
src/reader2/DApplySsm.cpp Normal file
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@ -0,0 +1,221 @@
/** @file DApplySsm.cpp
*
* @author Roland Conybeare, Feb 2026
**/
#include "DApplySsm.hpp"
#include <xo/reflectutil/typeseq.hpp>
//#include "parserstatemachine.hpp"
//#include "expect_expr_xs.hpp"
namespace xo {
using xo::reflect::typeseq;
namespace scm {
// ----- applyexprstatetype -----
const char *
applyexprstatetype_descr(applyexprstatetype x) {
switch (x) {
case applyexprstatetype::invalid: return "invalid";
case applyexprstatetype::apply_0: return "apply_0";
case applyexprstatetype::apply_1: return "apply_1";
case applyexprstatetype::apply_2: return "apply_2";
case applyexprstatetype::apply_3: return "apply_3";
case applyexprstatetype::N: break;
}
return "???applyexprstatetype";
}
std::ostream &
operator<<(std::ostream & os, applyexprstatetype x) {
os << applyexprstatetype_descr(x);
return os;
}
// ----- DApplySsm -----
DApplySsm::DApplySsm(obj<AExpression> fn_expr)
: applystate_{applyexprstatetype::apply_0},
fn_expr_{fn_expr}
{
if (fn_expr) {
this->applystate_ = applyexprstatetype::apply_1;
}
}
DApplySsm *
DApplySsm::make(DArena & mm,
obj<AExpression> fn_expr)
{
void * mem = mm.alloc(typeseq::id<DApplySsm>(),
sizeof(DApplySsm));
// TODO: revisit if we use flexible array for
// arguments
return new (mem) DApplySsm(fn_expr);
}
#ifdef NOT_YET
void
apply_xs::start(rp<Expression> fn_expr,
parserstatemachine * p_psm)
{
scope log(XO_DEBUG(p_psm->debug_flag()));
p_psm->push_exprstate(apply_xs::make());
p_psm->top_exprstate().on_expr(fn_expr.get(), p_psm);
p_psm->top_exprstate().on_leftparen_token(token_type::leftparen(), p_psm);
}
#endif
syntaxstatetype
DApplySsm::ssm_type() const noexcept {
return syntaxstatetype::apply;
}
std::string_view
DApplySsm::get_expect_str() const noexcept
{
switch(applystate_) {
case applyexprstatetype::invalid: return "invalid";
case applyexprstatetype::apply_0: return "expr";
case applyexprstatetype::apply_1: return "lparen";
case applyexprstatetype::apply_2: return "expr";
case applyexprstatetype::apply_3: return "comma|rparen";
case applyexprstatetype::N: break;
}
return "?expect";
}
#ifdef NOT_YET
void
apply_xs::on_expr(bp<Expression> expr,
parserstatemachine * p_psm)
{
scope log(XO_DEBUG(p_psm->debug_flag()));
switch (applyxs_type_) {
case applyexprstatetype::invalid:
case applyexprstatetype::n_applyexprstatetype:
// unreachable
break;
case applyexprstatetype::apply_0:
log && log("stash fn -> new state apply_1");
this->fn_expr_ = expr.promote();
this->applyxs_type_ = applyexprstatetype::apply_1;
return;
case applyexprstatetype::apply_1:
log && log("error: was expecting lparen");
// error, expecting lparen
break;
case applyexprstatetype::apply_2:
log && log(xtag("expr", expr), xtag("do", "stash expr -> new state apply_3"));
this->args_expr_v_.push_back(expr.promote());
this->applyxs_type_ = applyexprstatetype::apply_3;
return;
case applyexprstatetype::apply_3:
// error, expecting comma|rparen
break;
}
/* control here --implies-> error state */
constexpr const char * c_self_name = "apply_xs::on_expr";
const char * exp = this->get_expect_str();
this->illegal_input_on_expr(c_self_name, expr, exp, p_psm);
}
void
apply_xs::on_comma_token(const token_type & tk,
parserstatemachine * p_psm)
{
scope log(XO_DEBUG(p_psm->debug_flag()));
if (this->applyxs_type_ == applyexprstatetype::apply_3) {
this->applyxs_type_ = applyexprstatetype::apply_2;
expect_expr_xs::start(p_psm);
} else {
constexpr const char * c_self_name = "apply_xs::on_comma_token";
const char * exp = this->get_expect_str();
this->illegal_input_on_token(c_self_name, tk, exp, p_psm);
}
}
void
apply_xs::on_leftparen_token(const token_type & tk,
parserstatemachine * p_psm)
{
scope log(XO_DEBUG(p_psm->debug_flag()));
log && log("applyxs_type", applyxs_type_);
if (this->applyxs_type_ == applyexprstatetype::apply_1) {
this->applyxs_type_ = applyexprstatetype::apply_2;
expect_expr_xs::start(p_psm);
} else {
constexpr const char * c_self_name = "apply_xs::on_leftparen_token";
const char * exp = this->get_expect_str();
this->illegal_input_on_token(c_self_name, tk, exp, p_psm);
}
}
void
apply_xs::on_rightparen_token(const token_type & tk,
parserstatemachine * p_psm)
{
scope log(XO_DEBUG(p_psm->debug_flag()));
log && log("applyxs_type", applyxs_type_);
if (this->applyxs_type_ == applyexprstatetype::apply_3) {
/* (done) state */
log("apply complete -> pop + send expr");
rp<Apply> apply_expr = Apply::make(this->fn_expr_, this->args_expr_v_);
std::unique_ptr<exprstate> self = p_psm->pop_exprstate();
p_psm->top_exprstate().on_expr(apply_expr, p_psm);
return;
}
constexpr const char * c_self_name = "apply_xs::on_rightparen_token";
const char * exp = this->get_expect_str();
this->illegal_input_on_token(c_self_name, tk, exp, p_psm);
}
void
apply_xs::print(std::ostream & os) const
{
os << "<apply_xs"
<< xtag("this", (void*)this)
<< xtag("applyxs_type", applyxs_type_);
os << ">";
}
bool
apply_xs::pretty_print(const xo::print::ppindentinfo & ppii) const
{
return ppii.pps()->pretty_struct(ppii, "apply_xs",
refrtag("applyxs_type", applyxs_type_),
refrtag("fn_expr", fn_expr_),
refrtag("args_expr_v", args_expr_v_));
}
#endif
} /*namespace scm*/
} /*namespace xo*/
/* end DApplySsm.cpp */

7
src/reader2/DProgressSsm.cpp
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@ -538,7 +538,7 @@ namespace xo {
}
#endif
// here: have lhs_ expression
// here: have lhs_ expression
if (op_type_ == optype::invalid) {
// e.g. control here on input like
@ -911,12 +911,13 @@ namespace xo {
return;
}
if (optype_ == optype::invalid) {
if (op_type_ == optype::invalid) {
// leftparen begins function call arguments.
// .lhs_ now understood to be expression that evaluates to a
// function
}
Super::on_token(tk, p_psm);

2
src/reader2/syntaxstatetype.cpp
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@ -21,6 +21,8 @@ namespace xo {
return "ifelseexpr";
case syntaxstatetype::sequence:
return "sequence";
case syntaxstatetype::apply:
return "apply";
case syntaxstatetype::progress:
return "progress";
case syntaxstatetype::paren: