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add if

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This commit is contained in:
Pekka Laiho 2020-05-30 19:02:41 +07:00
parent 01e5c4b198
commit a4182f7d8e
1 changed files with 14 additions and 0 deletions
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14
src/Evaller.php
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@ -60,6 +60,20 @@ class Evaller
$value = $this->doEval($ast->get(2), $env);
return $env->set($ast->get(1)->getName(), $value);
} elseif ($ast->get(0)->getName() == 'if') {
if ($ast->count() < 3 || $ast->count() > 4) {
throw new MadLispException("if requires 2 or 3 arguments");
}
$result = $this->doEval($ast->get(1), $env);
if ($result == true) {
return $this->doEval($ast->get(2), $env);
} elseif ($ast->count() == 4) {
return $this->doEval($ast->get(3), $env);
} else {
return null;
}
} elseif ($ast->get(0)->getName() == 'let') {
if ($ast->count() != 3) {
throw new MadLispException("let requires exactly 2 arguments");