git ssb

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'use strict'
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var drain = require('./drain')
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module.exports = function reduce (/* reducer, acc, cb */) {
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  var reducer = arguments[0]
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  var acc
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  var cb
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  if (arguments.length === 3) {
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    acc = arguments[1]
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    cb = arguments[2]
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    return drain(function (data) {
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      acc = reducer(acc, data)
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    }, function (err) {
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      cb(err, acc)
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    })
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  } else {
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    cb = arguments[1]
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    var first = true
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    return drain(function (data) {
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      if (first) {
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        acc = data
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        first = false
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      } else {
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        acc = reducer(acc, data)
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      }
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    }, function (err) {
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      cb(err, acc)
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    })
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  }
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}
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