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added support for quasiquote

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This commit is contained in:
Pekka Laiho 2020-12-05 16:47:49 +07:00
parent 52b7bc6934
commit f4baaca01c
1 changed files with 60 additions and 0 deletions
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60
src/Evaller.php
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@ -277,6 +277,19 @@ class Evaller
}
return $astData[1];
} elseif ($symbolName == 'quasiquote') {
if ($astLength != 2) {
throw new MadLispException("quasiquote requires exactly 1 argument");
}
$ast = $this->quasiquote($astData[1]);
continue; // tco
} elseif ($symbolName == 'quasiquote-expand') {
if ($astLength != 2) {
throw new MadLispException("quasiquote-expand requires exactly 1 argument");
}
return $this->quasiquote($astData[1]);
}
}
@ -330,4 +343,51 @@ class Evaller
return $ast;
}
private function quasiquote($ast)
{
if ($ast instanceof MList) {
$data = $ast->getData();
// Check for unquote
if (count($data) > 0 && $data[0] instanceof Symbol && $data[0]->getName() == 'unquote') {
if (count($data) == 2) {
return $data[1];
} else {
throw new MadLispException("unquote requires exactly 1 argument");
}
}
$result = new MList();
for ($i = count($data) - 1; $i >= 0; $i--) {
$elt = $data[$i];
if ($elt instanceof MList && count($elt->getData()) > 0 && $elt->get(0) instanceof Symbol && $elt->get(0)->getName() == 'splice-unquote') {
if (count($elt->getData()) == 2) {
$result = new MList([
new Symbol('concat'),
$elt->get(1),
$result
]);
} else {
throw new MadLispException("splice-unquote requires exactly 1 argument");
}
} else {
$result = new MList([
new Symbol('pull'),
$this->quasiquote($elt),
$result
]);
}
}
return $result;
} elseif ($ast instanceof Symbol || $ast instanceof Collection) {
// Quote other forms which are affected by evaluation
return new MList([new Symbol('quote'), $ast]);
} else {
return $ast;
}
}
}