I was reading a paper about compression algorithm:
In order to optimality fit the line segments to the curve, Bellman's algorithm assumes that the input data is a valid (i.e., single-valued) function; thus, the trajectory cannot contain no loops.
What does it means with valid function? I suppose he intends to have a single-valued function, but: what's a single-valued function? According to wikipedia definition:
A single-valued function is an emphatic term for a mathematical function in the usual sense. That is, each element of the function's domain maps to a single, well-defined element of its range.
But this sounds to me like an injective function. Can you confirm that both (single-valued function and injective function) mean the same thing?