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xo-interpreter: scaffold interpreter read-eval-print loop

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This commit is contained in:
Roland Conybeare 2025-11-19 16:46:55 -05:00
commit 3956635920
7 changed files with 222 additions and 4 deletions
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98
xo-interpreter/src/interpreter/VirtualSchematikaMachine.cpp
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@ -4,9 +4,105 @@
#include "VsmInstr.hpp"
/** continue after completing a VSM instruction;
* achieve by jumping to continuation.
**/
//#define VSM_CONTINUE() this->pc_ = this->cont_; return;
namespace xo {
namespace scm {
struct VsmOps {
/** halt virtual scheme machine.
* This will cause innermost run() to return to its caller
**/
static VsmInstr halt_op;
/** evaluate an expression.
* - opcode is Opcode::eval
* - expression in register @ref expr_
**/
static VsmInstr eval_op;
};
VsmInstr
VsmOps::halt_op{VsmInstr::Opcode::halt, "halt"};
VsmInstr
VsmOps::eval_op{VsmInstr::Opcode::eval, "eval"};
VirtualSchematikaMachine::VirtualSchematikaMachine()
{}
void
VirtualSchematikaMachine::run()
{
for (const VsmInstr * pc = pc_; pc; pc = pc_)
this->execute_vsm(pc);
}
void
VirtualSchematikaMachine::execute_vsm(const VsmInstr * instr)
{
using Opcode = VsmInstr::Opcode;
switch (instr->opcode()) {
case Opcode::halt:
{
this->pc_ = nullptr;
this->cont_ = nullptr;
break;
}
case Opcode::eval:
{
/* generally speaking: opcode will be 1:1 with extypes */
switch (expr_->extype()) {
case exprtype::invalid:
case exprtype::constant:
case exprtype::primitive:
case exprtype::define:
case exprtype::assign:
case exprtype::apply:
case exprtype::lambda:
case exprtype::variable:
case exprtype::ifexpr:
case exprtype::sequence:
case exprtype::convert:
case exprtype::n_expr:
this->pc_ = nullptr;
this->value_ = nullptr;
this->error_ = SchematikaError(tostr("execute_vsm: not implmented",
xtag("extype", expr_->extype())));
this->cont_ = nullptr;
break;
}
}
break;
case Opcode::N_Opcode:
assert(false);
break;
}
}
std::pair<gp<Object>,
SchematikaError>
VirtualSchematikaMachine::eval(bp<Expression> expr)
{
this->pc_ = &VsmOps::eval_op;
this->expr_ = expr.promote();
this->cont_ = &VsmOps::halt_op;
this->run();
return std::make_pair(this->value_, this->error_);
}
} /*namespace scm*/
} /*namespace xo*/
/* end VirtualSchematikaMachine.hpp */
/* end VirtualSchematikaMachine.cpp */