Added sfclip2, a generalization of sfclip that allows independent specification of the upper and lower clip values. The upper and lower clip parameters default to FLT_MAX and -FLT_MAX so that no clipping occurs for a clip value that is not specified.

Added min and max options to sfstack to find the minimum or maximum values along an axis.

Added sflistminmax program to construct “incremental” minimum or maximum lists from an RSF file.
sflistminmax constructs the following set of minimum or maximum lists for each x2, x3, … xn in the input RSF file:
out[0] = in[0]
out[i] = min or max of (in[i], out[i-1]) for i = 1, 2, 3, … n1
sflistminmax mode=min can be used to simulate “erosion” for a set of geological surfaces, producing a new set of surfaces that do not cross.

Added sfminmax program to find the element-by-element minimum or maximum of two RSF files.