Advanced Programming Guide

262 • Chapter 6: Programming with Maple Graphicsthe only type of data the Maple plotting data structure accepts. Youmay also want to use the more efficient hardware floating-point calculationsrather than software floating-point operations, whenever possible.For more information on hardware floating-point operations, see the examplesin section 6.7. Instead of writing a procedure for computing thegrid, use the library function convert(..., gridpoints) which, in thecase of a single input, generates a structure of the following form. 3[ a.. b, c.. d, [ [z11, ... , z1n], ... ,[ zm1 , ... , zmn ] ] ]It uses either expressions or procedures as input. The output gives thedomain information a..b and c..d along with the z values of the inputthat it evaluates over the grid.> convert( sin(x*y), ’gridpoints’,> x=0..Pi, y=0..Pi, grid=[2, 3] );[0...3.14159265358979, 0...3.14159265358979, [[0., 0., 0.],[0., −0.975367972083633571, −0.430301217000074065]]]When xy > 0 and ln(−xy) is complex, the grid contains the valueundefined.> convert( (x,y) -> log(-x*y), ’gridpoints’,> 1..2, -2..1, grid=[2,3] );[1...2., −2...1., [[0.693147180559945286,−0.693147180559945286, undefined ],[1.386294361, 0., undefined ]]]Example 6 The version of vectorfieldplot makes use of the convert(...,gridpoints) procedure. The vectorfieldplot command should allow anumber of options. In particular, it should allow a grid = [m,n] option.You can accomplish this by passing the options to convert(...,gridpoints). The utility procedure makevectors handles the interfaceto convert(..., gridpoints).3 A two-dimensional Array is also allowed as the third argument. For more information,see the ?plot3d,structure help page.