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我正在通过 Alan Gates编写 Programming Pig，但在介绍宏功能的脚本中出现错误：http: //ofps.oreilly.com/titles/9781449302641/advanced_pig_latin.html#macros

--macro.pig
-- Given daily input and a particular year, analyze how
-- stock prices changed on days dividends were paid out.
define dividend_analysis (daily, year, daily_symbol, daily_open, daily_close)
returns analyzed {
divs          = load 'NYSE_dividends' as (exchange:chararray,
                    symbol:chararray, date:chararray, dividends:float);
divsthisyear  = filter divs by date matches '$year-.*';
dailythisyear = filter $daily by date matches '$year-.*';
jnd           = join divsthisyear by symbol, dailythisyear by $daily_symbol;
$analyzed     = foreach jnd generate dailythisyear::$daily_symbol,
                    $daily_close - $daily_open;
};

daily   = load 'NYSE_daily' as (exchange:chararray, symbol:chararray,
        date:chararray, open:float, high:float, low:float, close:float,
        volume:int, adj_close:float);
results = dividend_analysis(daily, '2009', 'symbol', 'open', 'close');

$错误是 .中的双冒号后出现的意外符号dailythisyear::$daily_symbol。

如果不替换该行，您将如何解决此问题：

$analyzed = foreach jnd generate divsthisyear::symbol, $daily_close - $daily_open;
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1 回答 1

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参数替换不能在宏内部使用。参数应显式传递给宏，参数替换仅在顶层使用。

您可以使用 -dryrun 命令行参数来查看宏是如何在线展开的。

所以无论如何你不能以这种方式在宏中使用参数。

于 2013-03-22T11:58:37.927 回答