Closes #2202

Improve pseudo-code for spatialDistribution

chapters/operatorsandexpressions.tex

@@ -735,7 +735,7 @@ \subsubsection{spatialDistribution}\doublelabel{spatialdistribution}
     out1:=interpolate(points, values, 1-(x-x0));
     out0:=values[1]; // similar to in0 but avoiding algebraic loop
   else
-    out0:=interpolate(points, values, (x-x0));
+    out0:=interpolate(points, values, 0-(x-x0));
     out1:=values[end]; // similar to in1 but avoiding algebraic loop
   end if;
   when <acceptedStep> then
@@ -745,14 +745,14 @@ \subsubsection{spatialDistribution}\doublelabel{spatialdistribution}
         m:=m-1;
       end while;
       values:=cat(1, {in0}, values[1:m], {interpolate(points, values,1-(x-x0))} );
-      points:=cat(1, {0}, points[1:m] .+ (x1-x0), {1} );
+      points:=cat(1, {0}, points[1:m] .+ (x-x0), {1} );
     elseif x<x0 then
       m:=1;
       while (if m<size(points,1) then points[m]+(x-x0)<=0 else false) then
         m:=m+1;
       end while;
       values:=cat(1, {interpolate(points, values, 0-(x-x0))},values[m:end],{in1});
-      points:=cat(1, {0}, points[m:end] .+ (x1-x0), {1});
+      points:=cat(1, {0}, points[m:end] .+ (x-x0), {1});
     end if;
     x0:=x;
   end when;