.NET/ASP.NET/C#/VB.NET PDF Document SDK

Figure 13-32. Four Analog Ins on solderless breadboard Using the PCF8591 in a NXT-G program requires importing the custom 8591 block. We prefer this PCF8591 block because it is simpler to use and seems more reliable than the one from Mindsensors. As you can see in Figure 13-33, the 8591 block has inputs for port number, I2C address, and analog output value. The values for the four channels of A/D values are displayed using the Display Value MyBlock developed in 2.

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[0] printfn "%s %s" itemOne itemTwo The results of this example, when compiled and executed, are as follows: one two To reference elements in rectangular arrays, use a period () followed by all the indexes in square brackets, separated by commas Unlike jagged arrays, which are multidimensional but can be defined using the same ([||]) syntax as single-dimensional arrays, you must create rectangular arrays with the create function of the Array2 and Array3 modules, which support two- and three-dimensional arrays, respectively This doesn t mean rectangular arrays are limited to three dimensions, because it s possible to use the SystemArray class to create rectangular arrays with more than three dimensions; however, creating such arrays should be considered carefully, because adding extra dimensions can quickly lead to very large objects The next example creates a rectangular array, square.

Then its elements are populated with the integers 1, 2, 3, and 4 #light let square = Array2create 2 2 0 square[0,0] <- 1 square[0,1] <- 2 square[1,0] <- 3 square[1,1] <- 4 printf "%A\r\n" square Now let s look at the differences between jagged and rectangular arrays First create a jagged array to represent Pascal s Triangle: #light let pascalsTriangle = [| [|1|]; [|1; 1|]; [|1; 2; 1|]; [|1; 3; 3; 1|];.

Figure 13-33. Read4 NXT-G program with 8591 block Without anything connected, channels 0 and 1 will read 255, as shown in Figure 13-34. You need to customize this design for your particular needs. You might want all potentiometer inputs, or you might want to connect four passive-style sensors. In 14, we ll show you how to combine the Four Analog Ins project with a graphics program to make a Pong video game.

During the development process you notice that one particular object on the calculation is failing If you re able to isolate the data source so that you re dealing with only a singular object or a small list of objects, you have no problem However, if you can reproduce the error only when using a large list of objects, and the failing object is toward the end of the list, then you have to set a breakpoint and step through it each time, looking for the particular object on which you know the error is occurring This scenario is quite easy to solve if using the conditional breakpoint functionality If you know the particular scenario that is failing, then you can write a conditional statement so that the breakpoint will suspend execution only when the condition is met Listing 7-1 shows a small snippet of simplistic JavaScript code.

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Figure 13-34. Read4 NXT-G program with 8591 block The Read4 NXC program shown in Listing 13-6 reads all four channels and just displays their values on the NXT display. This is a handy program for debugging PCF8591 sensors. Only the Auto increment bit is set in the control byte (hexadecimal 04) so it is in input Mode 0. ReadBuf[0] contains an old conversion value and is not displayed.

4; 5; 6; 7; 8;

All the code does is create an array of strings and iterate over the array, and for each string in the array, another string is prepended to the string This snippet of code shows how to conditionally stop the execution of the script based on a condition you define Listing 7-1 Iterating over a String Array function testBreakpointProperties() { var list = ["one", "two", "three", "four", "five", "six", "seven", "eight"]; var item = null; for(var i = 0; i < listlength; i++) { item = list[i]; item = "Text is: " + item; } } For this example, you ll want to suspend execution on only the seventh item in the list, which is the seven item.