/*!
* @fn partialSum
*
* @headerfile <seqan/parallel.h>
*
* @brief Computes the partial sum of a sequence.
*
* @signature TValue partialSum(target, source[, parallelTag]);
*
* @param[in] source A sequence of elements that should be partially summed. The
* sequence alphabet must support the <tt>operator+</tt> and
* conversion from zero, the type is <tt>TSource</tt>.
* @param[in] parallelTag Tag to enable/disable parallelism, one of
* <tt>Serial</tt>, <tt>Parallel</tt>, default is
* <tt>Serial</tt>.
* @param[out] target The resulting partial sum. This sequence will have the
* same length as <tt>source</tt> and contains at position
* <tt>i</tt> the sum of elements <tt>source[0]</tt>,
* <tt>source[1]</tt>, ..., <tt>source[i]</tt>.
*
* @return TValue The sum of all elements in <tt>source</tt>. The returned value
* equals the last value in target. <tt>TValue</tt> is
* <tt>Value<TSource>::Type</tt>.
*
* @see sum
*/