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start tail call optimization

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This commit is contained in:
Pekka Laiho 2020-06-04 21:26:00 +07:00
parent 291a7d6521
commit cb1a03e9bd
1 changed files with 168 additions and 146 deletions
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42
src/Evaller.php
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@ -3,8 +3,20 @@ namespace MadLisp;
class Evaller
{
private $p = null;
public function eval($ast, Env $env)
{
// Debug
if ($this->p == null) {
$this->p = new Printer();
}
print("eval: ");
$this->p->print($ast);
print("\n");
while (true) {
// Not list or empty list
if (!($ast instanceof MList)) {
return $this->evalAst($ast, $env);
@ -19,14 +31,15 @@ class Evaller
return true;
}
for ($i = 1; $i < $ast->count(); $i++) {
for ($i = 1; $i < $ast->count() - 1; $i++) {
$value = $this->eval($ast->get($i), $env);
if ($value == false) {
return $value;
}
}
return $value;
$ast = $ast->get($ast->count() - 1);
continue; // tco
} elseif ($ast->get(0)->getName() == 'case') {
if ($ast->count() < 2) {
throw new MadLispException("case requires at least 1 argument");
@ -61,11 +74,12 @@ class Evaller
throw new MadLispException("do requires at least 1 argument");
}
for ($i = 1; $i < $ast->count(); $i++) {
$value = $this->eval($ast->get($i), $env);
for ($i = 1; $i < $ast->count() - 1; $i++) {
$this->eval($ast->get($i), $env);
}
return $value;
$ast = $ast->get($ast->count() - 1);
continue; // tco
} elseif ($ast->get(0)->getName() == 'env') {
if ($ast->count() >= 2) {
if (!($ast->get(1) instanceof Symbol)) {
@ -109,9 +123,13 @@ class Evaller
$result = $this->eval($ast->get(1), $env);
if ($result == true) {
return $this->eval($ast->get(2), $env);
echo "if tco\n";
$ast = $ast->get(2);
continue;
} elseif ($ast->count() == 4) {
return $this->eval($ast->get(3), $env);
echo "if tco\n";
$ast = $ast->get(3);
continue;
} else {
return null;
}
@ -143,20 +161,23 @@ class Evaller
$newEnv->set($key->getName(), $val);
}
return $this->eval($ast->get(2), $newEnv);
$ast = $ast->get(2);
$env = $newEnv;
continue; // tco
} elseif ($ast->get(0)->getName() == 'or') {
if ($ast->count() == 1) {
return false;
}
for ($i = 1; $i < $ast->count(); $i++) {
for ($i = 1; $i < $ast->count() - 1; $i++) {
$value = $this->eval($ast->get($i), $env);
if ($value == true) {
return $value;
}
}
return $value;
$ast = $ast->get($ast->count() - 1);
continue; // tco
} elseif ($ast->get(0)->getName() == 'quote') {
if ($ast->count() != 2) {
throw new MadLispException("quote requires exactly 1 argument");
@ -178,6 +199,7 @@ class Evaller
$args = array_slice($ast->getData(), 1);
return $func->call($args);
}
}
private function evalAst($ast, Env $env)
{