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xo-interpreter: + expression sequences

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This commit is contained in:
Roland Conybeare 2025-11-26 00:32:37 -05:00
commit 7ee41a4b71
7 changed files with 158 additions and 4 deletions
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121
xo-interpreter/src/interpreter/VirtualSchematikaMachine.cpp
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@ -3,11 +3,13 @@
#include "VirtualSchematikaMachine.hpp"
#include "VsmInstr.hpp"
#include "ExpressionBoxed.hpp"
#include "xo/expression/ConstantInterface.hpp"
#include "xo/expression/Constant.hpp"
#include "xo/expression/DefineExpr.hpp"
#include "xo/expression/AssignExpr.hpp"
#include "xo/expression/Variable.hpp"
#include "xo/expression/IfExpr.hpp"
#include "xo/expression/Sequence.hpp"
#include "xo/object/Integer.hpp"
#include "xo/object/Boolean.hpp"
#include "xo/alloc/GC.hpp"
@ -24,6 +26,7 @@
namespace xo {
using xo::gc::GC;
using xo::obj::Integer;
using xo::obj::Boolean;
namespace scm {
@ -50,6 +53,12 @@ namespace xo {
* - top stack frame contains {ifexpr, cont}
**/
static VsmInstr complete_ifexpr_op;
/** proceed to next element of sequence-expr.
* - opcode is Opcode::complete_sequence
* - top stack fram contains {seq, next, cont}
*/
static VsmInstr complete_sequence_op;
};
VsmInstr
@ -64,6 +73,9 @@ namespace xo {
VsmInstr
VsmOps::complete_ifexpr_op{VsmInstr::Opcode::complete_ifexpr, "complete-ifexpr"};
VsmInstr
VsmOps::complete_sequence_op{VsmInstr::Opcode::complete_sequence, "complete-sequence"};
// ----- VirtualSchematikaMachineFlyweight -----
VirtualSchematikaMachineFlyweight::VirtualSchematikaMachineFlyweight(gc::IAlloc * mm,
@ -192,12 +204,16 @@ namespace xo {
this->eval_ifexpr_op();
break;
case exprtype::sequence:
log && log("eval -> sequence");
this->eval_sequence_op();
break;
case exprtype::invalid:
case exprtype::primitive:
case exprtype::apply:
case exprtype::lambda:
case exprtype::sequence:
case exprtype::convert:
case exprtype::n_expr:
this->pc_ = nullptr;
@ -218,6 +234,10 @@ namespace xo {
this->do_complete_ifexpr_op();
break;
case Opcode::complete_sequence:
this->do_complete_sequence_op();
break;
case Opcode::N_Opcode:
assert(false);
break;
@ -490,7 +510,12 @@ namespace xo {
if (test_value->value()) {
this->expr_ = ifexpr->when_true();
} else {
this->expr_ = ifexpr->when_false();
if (ifexpr->when_false()) {
this->expr_ = ifexpr->when_false();
} else {
/* 1-sided if-expr; evaluate to false */
this->expr_ = Constant<bool>::make(false);
}
}
this->stack_ = sp0->parent();
@ -507,6 +532,96 @@ namespace xo {
}
}
void
VirtualSchematikaMachine::eval_sequence_op()
{
using xo::scm::Sequence;
scope log(XO_DEBUG(true));
gc::IAlloc * mm = flyweight_.object_mm_;
/** must promote bp<Sequence> -> gp<ExpressionBoxed> **/
gp<ExpressionBoxed> seq_boxed = ExpressionBoxed::make(mm, expr_);
bp<Sequence> seq = Sequence::from(expr_);
assert(seq.get());
assert(env_.get());
this->pc_ = &VsmOps::eval_op;
if (seq->size() == 0) {
/* for 0-size sequence, invent an expression */
this->expr_ = Constant<bool>::make(false);
} else {
this->expr_ = (*seq)[0];
}
if (seq->size() > 1) {
/* remainder */
gp<Integer> next = Integer::make(mm, 1);
/* when control arrives at .cont_ will have:
* .value_ -> result of evaluating last expr in seq
*/
this->stack_ = VsmStackFrame::push2(mm, stack_, seq_boxed, next, cont_);
/* .stack_:
* frame
* [0] = seq (boxed sequence)
* [1] = next (index of next seq member to evaluate)
* ..
*/
this->cont_ = &VsmOps::complete_sequence_op;
} else {
/* sequence completes when expr_ evaluated
* -> proceed with o.g. cont_
*/
}
}
void
VirtualSchematikaMachine::do_complete_sequence_op()
{
using xo::scm::Sequence;
scope log(XO_DEBUG(true));
/* - stack: top frame has 2 slots:
* [0] : seq (boxed Sequence)
* [1] : next (index of next seq element to eval
*/
assert(value_.get());
assert(stack_.get());
gp<VsmStackFrame> sp0 = this->stack_;
assert(sp0->size() == 2);
bp<Sequence> seq = Sequence::from(ExpressionBoxed::from((*sp0)[0])->contents());
gp<Integer> next_obj = Integer::from((*sp0)[1]);
size_t i_next = next_obj->value();
assert(i_next < seq->size());
this->pc_ = &VsmOps::eval_op;
this->expr_ = (*seq)[i_next];
if (i_next + 1 == seq->size()) {
/* last member of sequence -> tail call optimization */
this->stack_ = sp0->parent();
this->cont_ = sp0->continuation();
} else {
/* we can modify next_obj in place,
* since it's unique to frame sp0
*/
next_obj->assign_value(i_next + 1);
this->cont_ = &VsmOps::complete_sequence_op;
}
}
} /*namespace scm*/
} /*namespace xo*/