Context - Error creating boxes in loop

Question

The following code creates an array of boxes to represent an array.

\startMPinclusions
 input boxes ;
\stopMPinclusions

\starttext
\startluacode
function createGraphic(k,c,indH)
    local i=1
    local j=65
    context.startuseMPgraphic(name)
    context("boxjoin(a.se=b.sw; a.ne=b.nw);")
    while k[i] do
        bname=string.char(j)
        context("boxit."..bname.."(btex "..k[i].." etex)("..c[i]..");drawboxed("..bname..");")
        i=i+1
        j=j+1
    end
     context.stopuseMPgraphic()
    context.useMPgraphic(name)
end

a={51,31,4,22,23,45,23,43,54,22,11,34}
colors={"blue","blue","blue","blue","blue","blue","blue","blue","blue","white","white","white"}
createGraphic(a,colors)

The output is

Now I want to change the colors dynamically and call the createGraphic() in a loop. So I wrote the following function to change the colors array.

function refreshColors(yellowEndIndex,redIndex,blueIndex)
        print(yellowEndIndex..","..redIndex..","..blueIndex)
        local ccnt=1
        while a[ccnt] do
                if ccnt < yellowEndIndex then
                    colors[ccnt] = "yellow"
                elseif ccnt == redIndex then
                    colors[ccnt] = "red"
                elseif ccnt == blueIndex then
                    colors[ccnt] = "blue"
                else
                    colors[ccnt] = "white"
                end
                ccnt= ccnt+1
        end
end
refreshColors(2,4,6)
createGraphic(a,colors)

Now, the output is

Also when I call refreshColors() in loop and createGraphic() outside there is no error.

for i=1,10,1 do
    refreshColors(i,0,0)
end
createGraphic(a,colors)

Now the output is

However, when I call createGraphic() inside loop, error occurs.

for i=1,10,1 do
    refreshColors(i,0,0)
 createGraphic(a,colors)
end

The error message thrown by Texworks is

error on line 33 in file try.tex: terminal: ! Inconsistent equation (off by -1).

Line 33 is

colors[ccnt] = "red"

Here is the link to the boxes.mp used in the program.

I want to call the createGraphic() inside the loop. Why the error occurs??

Answer 1

The problem must be with boxes.mp In the macro boxit, replace

@#col = cellColor;

with

@#col := cellColor;

This might make it work..