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add special constants __FILE__ and __DIR__

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This commit is contained in:
Pekka Laiho 2020-10-24 12:27:28 +07:00
parent c110522f3b
commit 2f48754902
4 changed files with 46 additions and 17 deletions
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4
README.md
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@ -362,11 +362,13 @@ odd? | Return true if the argument is odd number (1, 3, 5, ...).
The following constants are defined by default:
Name | PHP constant
------- | ------------
-------- | ------------
DIRSEP | DIRECTORY_SEPARATOR
HOME | $_SERVER['HOME']
EOL | PHP_EOL
PI | M_PI
__DIR__ | Directory of a file being evaluated using the special form `load`. Otherwise null.
__FILE__ | Filename of a file being evaluated using the special form `load`. Otherwise null.
## Extending

9
src/Env.php
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@ -37,13 +37,8 @@ class Env extends Hash
return $this->parent;
}
public function set(string $key, $value)
public function getRoot(): ?Env
{
// Do not allow overwriting values in root env
if ($this->has($key) && $this->parent == null) {
throw new MadLispException("attempt to overwrite $key in root env");
}
return parent::set($key, $value);
return $this->parent ? $this->parent->getRoot() : $this;
}
}

36
src/Evaller.php
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@ -87,8 +87,16 @@ class Evaller
throw new MadLispException("first argument to def is not symbol");
}
$name = $ast->get(1)->getName();
// Do not allow reserved symbols to be defined
$reservedSymbols = ['__FILE__', '__DIR__'];
if (in_array($name, $reservedSymbols)) {
throw new MadLispException("def reserved symbol $name");
}
$value = $this->eval($ast->get(2), $env);
return $env->set($ast->get(1)->getName(), $value);
return $env->set($name, $value);
} elseif ($ast->get(0)->getName() == 'do') {
if ($ast->count() == 1) {
return null;
@ -199,22 +207,42 @@ class Evaller
throw new MadLispException("load requires exactly 1 argument");
}
$filename = $ast->get(1);
// We have to evaluate the argument, it could be a function
$filename = $this->eval($ast->get(1), $env);
if (!is_string($filename)) {
throw new MadLispException("first argument to load is not string");
} elseif (!is_readable($filename)) {
}
// Replace ~ with user home directory
// Expand relative path names into absolute
$targetFile = realpath(str_replace('~', $_SERVER['HOME'], $filename));
if (!$targetFile || !is_readable($targetFile)) {
throw new MadLispException("unable to read file $filename");
}
$input = @file_get_contents($filename);
$input = @file_get_contents($targetFile);
// Wrap input in a do to process multiple expressions
$input = "(do $input)";
$expr = $this->reader->read($this->tokenizer->tokenize($input));
// Handle special constants
$rootEnv = $env->getRoot();
$prevFile = $rootEnv->get('__FILE__');
$prevDir = $rootEnv->get('__DIR__');
$rootEnv->set('__FILE__', $targetFile);
$rootEnv->set('__DIR__', dirname($targetFile) . \DIRECTORY_SEPARATOR);
// Evaluate the contents
$ast = $this->eval($expr, $env);
// Restore the special constants to previous values
$rootEnv->set('__FILE__', $prevFile);
$rootEnv->set('__DIR__', $prevDir);
continue; // tco
} elseif ($ast->get(0)->getName() == 'or') {
if ($ast->count() == 1) {

4
src/LispFactory.php
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@ -13,6 +13,10 @@ class LispFactory
// Root environment
$env = new Env('root');
// Register special constants
$env->set('__FILE__', null);
$env->set('__DIR__', null);
// Register core functions
$env->set('doc', new CoreFunc('doc', 'Get documentation for a function.', 1, 1,
function ($a) {