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PostMaster.h
expressionclassifier.cpp 13.29 KiB
#include <iostream>
#include <cmath>
#include "error.hpp"
#include "expressionclassifier.hpp"
#include "modccutil.hpp"
// this turns out to be quite easy, however quite fiddly to do right.
// default is to do nothing and return
void ExpressionClassifierVisitor::visit(Expression *e) {
throw compiler_exception(" attempting to apply linear analysis on " + e->to_string(), e->location());
}
// number expresssion
void ExpressionClassifierVisitor::visit(NumberExpression *e) {
// save the coefficient as the number
coefficient_ = e->clone();
}
// identifier expresssion
void ExpressionClassifierVisitor::visit(IdentifierExpression *e) {
// check if symbol of identifier matches the identifier
if(symbol_ == e->symbol()) {
found_symbol_ = true;
coefficient_.reset(new NumberExpression(Location(), "1"));
}
else {
coefficient_ = e->clone();
}
}
/// unary expresssion
void ExpressionClassifierVisitor::visit(UnaryExpression *e) {
e->expression()->accept(this);
if(found_symbol_) {
switch(e->op()) {
// plus or minus don't change linearity
case tok::minus :
coefficient_ = unary_expression(Location(),
e->op(),
std::move(coefficient_));
return;
case tok::plus :
return;
// one of these applied to the symbol certainly isn't linear
case tok::exp :
case tok::cos :
case tok::sin :
case tok::log :
is_linear_ = false;
return;
default :
throw compiler_exception(
"attempting to apply linear analysis on unsuported UnaryExpression "
+ yellow(token_string(e->op())), e->location());
}
}
else {
coefficient_ = e->clone();
}
}
// binary expresssion
// handle all binary expressions with one routine, because the
// pre-order and in-order code is the same for all cases
void ExpressionClassifierVisitor::visit(BinaryExpression *e) {
bool lhs_contains_symbol = false;
bool rhs_contains_symbol = false;
expression_ptr lhs_coefficient; expression_ptr rhs_coefficient;
expression_ptr lhs_constant;
expression_ptr rhs_constant;
// check the lhs
reset();
e->lhs()->accept(this);
lhs_contains_symbol = found_symbol_;
lhs_coefficient = std::move(coefficient_);
lhs_constant = std::move(constant_);
if(!is_linear_) return; // early return if nonlinear
// check the rhs
reset();
e->rhs()->accept(this);
rhs_contains_symbol = found_symbol_;
rhs_coefficient = std::move(coefficient_);
rhs_constant = std::move(constant_);
if(!is_linear_) return; // early return if nonlinear
// mark symbol as found if in either lhs or rhs
found_symbol_ = rhs_contains_symbol || lhs_contains_symbol;
if( found_symbol_ ) {
// if both lhs and rhs contain symbol check that the binary operator
// preserves linearity
// note that we don't have to test for linearity, because we abort early
// if either lhs or rhs are nonlinear
if( rhs_contains_symbol && lhs_contains_symbol ) {
// be careful to get the order of operation right for
// non-computative operators
switch(e->op()) {
// addition and subtraction are valid, nothing else is
case tok::plus :
case tok::minus :
coefficient_ =
binary_expression(Location(),
e->op(),
std::move(lhs_coefficient),
std::move(rhs_coefficient));
return;
// multiplying two expressions that depend on symbol is nonlinear
case tok::times :
case tok::pow :
case tok::divide :
default :
is_linear_ = false;
return;
}
}
// special cases :
// operator | invalid symbol location
// -------------------------------------
// pow | lhs OR rhs
// comparisons | lhs OR rhs
// division | rhs
////////////////////////////////////////////////////////////////////////
// only RHS contains the symbol
////////////////////////////////////////////////////////////////////////
else if(rhs_contains_symbol) {
switch(e->op()) {
case tok::times :
// determine the linear coefficient
if( rhs_coefficient->is_number() &&
rhs_coefficient->is_number()->value()==1) {
coefficient_ = lhs_coefficient->clone();
}
else {
coefficient_ =
binary_expression(Location(), tok::times,
lhs_coefficient->clone(),
rhs_coefficient->clone());
}
// determine the constant
if(rhs_constant) {
constant_ =
binary_expression(Location(),
tok::times,
std::move(lhs_coefficient),
std::move(rhs_constant));
} else {
constant_ = nullptr;
}
return;
case tok::plus :
// constant term
if(lhs_constant && rhs_constant) {
constant_ =
binary_expression(Location(),
tok::plus,
std::move(lhs_constant),
std::move(rhs_constant));
}
else if(rhs_constant) {
constant_ = binary_expression(Location(),
tok::plus,
std::move(lhs_coefficient),
std::move(rhs_constant));
}
else {
constant_ = std::move(lhs_coefficient);
}
// coefficient
coefficient_ = std::move(rhs_coefficient);
return;
case tok::minus :
// constant term
if(lhs_constant && rhs_constant) {
constant_ = binary_expression(Location(),
tok::minus,
std::move(lhs_constant),
std::move(rhs_constant));
}
else if(rhs_constant) {
constant_ = binary_expression(Location(),
tok::minus,
std::move(lhs_coefficient),
std::move(rhs_constant));
}
else {
constant_ = std::move(lhs_coefficient);
}
// coefficient
coefficient_ = unary_expression(Location(),
e->op(),
std::move(rhs_coefficient));
return;
case tok::pow :
case tok::divide :
case tok::lt :
case tok::lte :
case tok::gt :
case tok::gte :
case tok::equality :
is_linear_ = false;
return;
default:
return;
} }
////////////////////////////////////////////////////////////////////////
// only LHS contains the symbol
////////////////////////////////////////////////////////////////////////
else if(lhs_contains_symbol) {
switch(e->op()) {
case tok::times :
// check if the lhs is == 1
if( lhs_coefficient->is_number() &&
lhs_coefficient->is_number()->value()==1) {
coefficient_ = rhs_coefficient->clone();
}
else {
coefficient_ =
binary_expression(Location(),
tok::times,
std::move(lhs_coefficient),
std::move(rhs_coefficient));
}
// constant term
if(lhs_constant) {
constant_ = binary_expression(Location(),
tok::times,
std::move(lhs_constant),
std::move(rhs_coefficient));
} else {
constant_ = nullptr;
}
return;
case tok::plus :
coefficient_ = std::move(lhs_coefficient);
// constant term
if(lhs_constant && rhs_constant) {
constant_ = binary_expression(Location(),
tok::plus,
std::move(lhs_constant),
std::move(rhs_constant));
}
else if(lhs_constant) {
constant_ = binary_expression(Location(),
tok::plus,
std::move(lhs_constant),
std::move(rhs_coefficient));
}
else {
constant_ = std::move(rhs_coefficient);
}
return;
case tok::minus :
coefficient_ = std::move(lhs_coefficient);
// constant term
if(lhs_constant && rhs_constant) {
constant_ = binary_expression(Location(),
tok::minus,
std::move(lhs_constant),
std::move(rhs_constant));
}
else if(lhs_constant) {
constant_ = binary_expression(Location(),
tok::minus,
std::move(lhs_constant),
std::move(rhs_coefficient));
}
else {
constant_ = unary_expression(Location(),
tok::minus,
std::move(rhs_coefficient));
}
return;
case tok::divide: coefficient_ = binary_expression(Location(),
tok::divide,
std::move(lhs_coefficient),
rhs_coefficient->clone());
if(lhs_constant) {
constant_ = binary_expression(Location(),
tok::divide,
std::move(lhs_constant),
std::move(rhs_coefficient));
}
return;
case tok::pow :
case tok::lt :
case tok::lte :
case tok::gt :
case tok::gte :
case tok::equality :
is_linear_ = false;
return;
default:
return;
}
}
}
// neither lhs or rhs contains symbol
// continue building the coefficient
else {
coefficient_ = e->clone();
}
}
void ExpressionClassifierVisitor::visit(CallExpression *e) {
for(auto& a : e->args()) {
a->accept(this);
// we assume that the parameter passed into a function
// won't be linear
if(found_symbol_) {
is_linear_ = false;
return;
}
}
}