PHP Expression::Render方法代码示例

 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];
}