public static function EmitExpression($expr)
{
if ($expr === NULL || $expr === FALSE || is_array($expr) && empty($expr)) {
return 'NULL';
}
if ($expr === TRUE) {
return 'true';
}
if (is_int($expr) || is_double($expr)) {
return (string) $expr;
}
if (is_string($expr)) {
return "'" . addslashes($expr) . "'";
}
if (is_array($expr)) {
$out = array();
foreach ($expr as $e) {
$out[] = self::EmitExpression($e);
}
return 'array(' . implode(', ', $out) . ')';
}
if ($expr instanceof Tilde) {
return 'new Tilde()';
}
if ($expr instanceof AtSign) {
return 'new AtSign()';
}
if ($expr instanceof Symbol) {
return "Symbol::Make('{$expr->name}')";
}
if ($expr instanceof Lambda) {
return '<lambda:' . Expression::Render($expr->arguments) . '>';
}
if ($expr instanceof Macro) {
return '<macro:' . Expression::Render($expr->arguments) . '>';
}
return '<' . get_class($expr) . '>';
}
public function Evaluate($sexp)
{
//echo "EVAL: " . Expression::Render($sexp) . "\n";
if ($sexp instanceof Symbol) {
if (($r = @$this->environment[$sexp->name]) !== NULL) {
return $r === FALSE ? NULL : $r;
}
var_dump($sexp);
throw new Exception("Unknown identifier: " . $sexp->name);
} elseif (!is_array($sexp)) {
return $sexp;
}
if (empty($sexp)) {
return NULL;
}
$lambda = $sexp[0];
$args = array_slice($sexp, 1);
if (is_array($lambda)) {
$evald = $this->Evaluate($lambda);
//echo Expression::Render($lambda) . " ~~> " . Expression::Render($evald) . "\n";
$lambda = $evald;
}
if ($lambda instanceof Symbol && ($val = @$this->environment[$lambda->name]) !== NULL) {
$lambda = $val;
}
$phpName = NULL;
if ($lambda instanceof Symbol) {
$phpName = ($in = @self::$_internalNames[$lambda->name]) === NULL ? str_replace('-', '_', $lambda->name) : $in;
}
if ($lambda instanceof Macro) {
$list = NULL;
foreach ($lambda->expressions as $e) {
// macro-expansion-time
$applied = $lambda->arguments === NULL ? $e : $this->Apply($e, $lambda->arguments, $args);
//echo Expression::Render($e) . " =APPLY=> " . Expression::Render($applied) . "\n";
$expanded = $this->Evaluate($applied);
//echo Expression::Render($applied) . " =MACROEXPAND=> " . Expression::Render($expanded) . "\n";
}
return $this->Evaluate($expanded);
}
if ($lambda instanceof Symbol) {
// special forms (non-evaluated parameters)
$specialForm = "lizp_special_form_{$phpName}";
if (function_exists($specialForm)) {
return call_user_func($specialForm, $this, $args);
}
}
// We evaluate the parameters
$params = array();
$expandNext = FALSE;
foreach ($args as $v) {
if ($v instanceof AtSign) {
$expandNext = TRUE;
continue;
}
$r = $this->Evaluate($v);
if ($expandNext && is_array($r)) {
$params = array_merge($params, $r);
} else {
$params[] = $r;
}
$expandNext = FALSE;
}
if ($lambda instanceof Lambda) {
$r = NULL;
foreach ($lambda->expressions as $e) {
$args = array();
foreach ($params as $i) {
if (is_array($i)) {
$i = array(Symbol::Make('quote'), $i);
}
$args[] = $i;
}
//$params = $args;
$applied = $lambda->arguments === NULL ? $e : $this->Apply($e, $lambda->arguments, $params);
//echo Expression::Render($e) . " -APPLY-> " . Expression::Render($applied) . "\n";
$r = $this->Evaluate($applied);
//echo Expression::Render($applied) . " -EVAL-> " . Expression::Render($r) . "\n";
}
return $r;
}
if ($lambda instanceof Symbol) {
// internal functions / php functions
$internalFn = "lizp_internal_fn_{$phpName}";
if (($isInternal = function_exists($internalFn)) || function_exists($phpName)) {
if ($isInternal) {
return call_user_func($internalFn, $this, $params);
}
$r = call_user_func_array($phpName, $params);
if ($r === FALSE || is_array($r) && empty($r)) {
$r = NULL;
}
return $r;
}
}
throw new Exception("Unable to evaluate Expression: " . Expression::Render($sexp) . " because function name evaluates to " . Expression::Render($lambda));
}
function lizp_special_form_dump($env, $args)
{
foreach ($args as $arg) {
echo Expression::Render($arg) . "\n";
}
return NULL;
}
function lizp_internal_fn_parse($env, $args)
{
if (!is_string(@$args[0])) {
throw new Exception("Syntax Error: (PARSE <string>)");
}
$expr = Expression::NewParse($args[0]);
if (count($expr) > 1) {
throw new Exception("Error: Multiple expressions given in " . Expression::Render($arg[0]));
}
return @$expr[0];
}