Machine Problem 2, due Sept 25

Part of the homework for CS:2820, Fall 2017
by Douglas W. Jones
THE UNIVERSITY OF IOWA Department of Computer Science

Write a Java program, in file that can be run as follows, assuming that there is a file called f in your current directory:

[HawkID@serv15 project]$ java Logic f

When your program is run using the above command, it should read a description of a network of logic gates and wires from the file f (the file name provided on the command line). Here is an example description:

gate A and 1.0
gate B or 0.5
wire A out B in1 0.1
wire B out A in1 0.3
-- another gate
gate C neg 0.5

wire A out C in 0.1
wire C out B in2 0.1

For gates, the arguments in the source file are, from left to right:

For wires, the arguments are, from left to right:

Note in the above that we don't use punctuation to indicate a pin of a gate, for example, A.out, we just use a space.

A significant part of this assignment is that your program must tolerate and appropriately report errors in the input. That is, numbers must be given where expected, no gate name may be defined more than once, all gate names referenced in wire descriptions must have been declared before use, no input pin of a gate may also be used as an output, and no input pin may be used more than once.

If and only if there are no errors in the input, your program should generate as output to standard output (System.out) a reconstruction of the the input, although the order of gates and wires in the output may be changed, spacing may be standardized, and comments may be lost. Furthermore, numeric fields may be output in equivalent form — so for example, 05.6 or 5.600 might bothe end up being output as 5.6.

Error messages should be output to standard error (System.error) and should reasonably document the error, for example:

cannot open file named xyzzl.bug
shoe found where gate or wire expected
gate X illegally redefined
wire X out Y in undefined source
wire X Z delay expected

When there are errors, the output to standard output should include all correct parts of the input and, if it includes incorrect parts, those should make sense. The format of the error messages and the output of incorrect parts of the input are deliberately underspecified. You have design decisions to make here.

Note: For now, the count of the number of inputs permitted on a gate is just a number. Later, we will add code to enforce this: A 3 input gate must have exactly 3 wires to its inputs, and we will eliminate this field on gates that only have one input (neg, for example). If you want extra work, try enforcing this.

Grading criteria: No credit will be given to programs that do not represent a substantial attempt at meeting the requirements of this assignment. Your program must:

Note that MP3 will involve extending MP2 to support gates with specific named inputs and outputs, so planning for this, while not part of this assignment, may simplify the next.

Note that the requirements for header comments in the file header are absolute. Your name must appear in the form that it appears on your ID card. The TAs will not waste their time doing detective work to attempt to figure out who submitted what code.

Submission: Your solution should consist of a single file named, with one public method, main. (We will chop the file into smaller more managable pieces later, as it grows.)

To submit your solution, use the submit shell command while your current directory is the one holding the source file. The dialogue with the submit command will be similar to that you used with MP1, except that you will use mp2 wherever you used mp1 in that dialogue.