## There is a basic error in the shop9.js-e construal 
## The dependency that links the price tag associated with an item with its price is missing
## To confirm this omission, use a Dependency Map to search for a chain of dependencies from price1 to item1text 
## The file of functions and definitions below records the basic updates needed to implement this dependency
## The Dependency Map view will show how the dependencies are reconfigured dynamically as the updates are made

## The function pricedisplay() is updated so that a change in the value of the observable 'items' affects item1text 

func pricedisplay {
	para ix,items;
	if (ix==1) return displaycurrency(items[1][2]);
	if (ix==2) return displaycurrency(items[2][2]);
	if (ix==3) return displaycurrency(items[3][2]);
	if (ix==4) return displaycurrency(items[4][2]);
	if (ix==5) return displaycurrency(items[5][2]);
	if (ix==6) return displaycurrency(items[6][2]);
}

## this very clumsy function definition can be refined: 

func pricedisplay {
	para ix,items;
	return displaycurrency(items[ix][2]);
}

## the addition of a second parameter to pricedisplay() has to be reflected in the associated definitions:

item1text is Text(pricedisplay(1, items), 0.6*scaleWidth,5*scaleWidth);
item2text is Text(pricedisplay(2, items), 1.9*scaleWidth,5*scaleWidth);
item3text is Text(pricedisplay(3, items), 3.2*scaleWidth,5*scaleWidth);
item4text is Text(pricedisplay(4, items), 4.5*scaleWidth,5*scaleWidth);
item5text is Text(pricedisplay(5, items), 5.8*scaleWidth,5*scaleWidth);
item6text is Text(pricedisplay(6, items), 7.1*scaleWidth,5*scaleWidth);

## you can test the update so far thus:

price1 = 0.31; price2 = 1.64; price3 = 0.39; price4 = 2.0; price5 = 0.29; price6 = 0.42;

## problematic aspects of JavaScript floating point arithmetic lead to inappropriate displays of prices:

## to resolve these the function displaycurrency() has to be modified so that the round() function is introduced:

func displaycurrency {
	para amount;
	auto pounds, pence;
	pence = 100*amount;
	pounds = int (pence / 100);
	pence = round(pence - pounds*100);
	return decodeHTML("£") // ((pounds>0) ? str(pounds) : "0") // ((pence>0) ? "-" //  str(pence)  // "p" : "");
}

## the update then works correctly:

price1 = 0.31; price2 = 1.64; price3 = 0.39; price4 = 2.0; price5 = 0.29; price6 = 0.42;