1. A method, comprising: performing, by a processor: receiving an operand vector, a basis vector, a selection vector, and a control vector; selecting a basis value from the basis vector dependent upon the selection vector; and generating a result vector dependent upon the selected basis value; wherein each of the operand vector, the basis vector, the selection vector, the control vector, and the result vector includes a respective plurality of elements that occupy N ordered element positions, wherein the N ordered element positions include an initial element position and a last element position; wherein N is an integer greater than one; wherein for each given one of the N ordered element positions, said generating comprises performing a shift operation dependent on selected elements of the operand vector that are selected dependent upon the control vector and the basis value, such that for a particular one of the N ordered element positions, performing the shift operation for the particular element position is dependent upon one or more element positions prior to the particular element position.