Wright State University Department of Computer Science and Engineering CS 780 Fall 2010 Prasad Assignment 1 Due Sept 22 10 pts This assignment asks you to write a short Cool program The purpose is to acquaint you with the Cool language and to give you experience with some of the tools used in the course In this assignment you are to implement a very simple type inference engine for postfix expressions in Cool The input is a sequence of postfix expressions built using integer variables i and j real variables a and b and overloaded binary operators and The output is the sequence of inferred types To accomplish this task you can use a stack as follows A machine with only a single stack for storage is a stack machine Consider the following very primitive language for programming a stack machine and the corresponding action for inferring types Command i j a b q Meaning push int on the stack push int on the stack push real on the stack push real on the stack infer the type of the associated postfix expression using the top two stack entries and pushing the result type back on stack print contents of the stack top quit Here are some additional details The i and j commands simply push the string int on top of the stack The a and b commands simply push the string real on top of the stack The behavior of the resp command is to pop the top two stack entries corresponding to the two sub expresssions and to push the type of the resulting postfix expression on the stack Specifically the type of e1 op e2 is int if both the sub expressions e1 and e2 are of type int otherwise it is real The command prints the contents of the stack top The following examples show the effect of the various commands the input is read from left to right and the top of the stack is on the left that is stack values are the mirror image of the corresponding input expression types input stack j i int a i j int real a b i real i b real int Furthermore the command has the side effect of printing the type of b real You are to implement this translator in Cool Input to the program is a series of commands one command per line Your interpreter should prompt for commands with To simplify coding your program need not do any sophisticated error checking However it is always a good idea to write robust programs to facilitate debugging You are free to implement this program in any style you choose However in preparation for building a Cool compiler we recommend that you try to develop an object oriented solution One approach is to define a class Stack of strings with suitable operations 1 We wrote a robust solution using about 120 lines of formatted Cool source code This information is provided to you as a rough measure of the amount of work involved in the assignment your solution may be either shorter or substantially longer Sample session The following is a sample compile and run of our solution on gandalf cs wright edu gandalf coolc type cl gandalf spim file type s SPIM Version 6 3a of January 14 2001 Copyright 1990 2000 by James R Larus larus cs wisc edu All Rights Reserved See the file README for a full copyright notice spim parser immediate value 4 out of range 0 65535 on andi gp gp 0xfffffffc word align gp spim parser immediate value 4 out of range 0 65535 on andi a0 a0 0xFFFFFFFC spim parser immediate value 4 out of range 0 65535 on andi gp gp 0xfffffffc spim parser immediate value 4 out of range 0 65535 on andi t1 t1 0xFFFFFFFC Loaded usr local lib cool lib trap handler Warning local symbol main was not defined a i j int real q COOL program successfully executed line 806 of file usr local lib cool li line 870 of file usr local lib cool li line 990 of file usr local lib cool li line 1680 of file usr local lib cool l The executables coolc and spim are compiled for the SPARC Solaris and installed on gandalf cs wright edu in the directory usr local lib cool bin As it stands due to some incompatibilities between the expectations of standard spim and the changes to spim to run Cool there are benign error messages complaining about immediate value 4 out of range 0 65535 and about main being undefined Ignore them for this assignment Important You should make sure to place usr local lib cool bin at the beginning in your path variable setting to use the executables meant for this assignment To change the path variable add the line setenv PATH usr local lib cool bin PATH at the end of your login file or tcshrc file if you use tcsh add the line 2 path usr local lib cool bin path export path at the end of your profile file or bashrc file if you use bash The assembly code for a working version of type cl is in the file type eg s Login to gandalf and run as shown in the example above You can compare the results from your program with the results of type eg s to test whether your program is operating correctly You can run on a test input file as follows spim file type eg s type test Getting and turning in the assignment Create a working directory and cd into it From there at the prompt gandalf type gandalf make f usr local lib cool assignments PA1 Makefile This command creates several files you will need in the directory Follow the directions in the README file which explains how to turn in your assignment when you are finished it also contains a few questions you are to answer as part of the assignment Upon turning in your program you will receive an automatic email acknowledgement providing a long listing of copied files 3