A grid function is a function defined on a grid at one or more times. Some examples of grid function declarations are:
float A on g1 at -1,0,1 int B on g2 at 0,1 float C on g1 float D on g2 at -1,0,1 alias float E on g3 at 0,1 "Electric Field"
First comes the grid function type, either float or int. Next comes the name followed by the reserved word on and the grid name on which the function is defined. If the declaration stopped here (such as that for C above), we get a single time level. Adding the reserved word at followed by a list of offsets (positive or negative integers) gives a function defined on one time level for each offset. For instance the definition for A would give a three time level function defined at times n-1 , n , and n+1. Next comes the optional reserved word alias which declares common storage for the first and last time levels. Following any of these declarations can be a string which is used as a ``print name'' for the grid function. Uses for the print name will be explained in chapter 2.