1. A method, comprising: performing, by a processor: receiving an operand vector and a control vector; and generating a result vector; wherein each of the operand vector, the control vector, and the result vector includes a respective plurality of elements that occupy N ordered element positions; wherein for each given one of the N ordered element positions, said generating comprises performing a Boolean operation dependent upon selected elements of the operand vector that are selected dependent upon the control vector, such that for a particular one of the N ordered element positions, performing the Boolean operation for the particular element position is dependent upon one or more element positions prior to the particular element position.