The third project involves modifying the attached interpreter so that it interprets programs for the complete language.

CMSC 430 Project 3The third project involves modifying the attached interpreter so that it interprets programs for thecomplete language.You may convert all values to double values, although you can maintain their individual types ifyou wish.When the program is run on the command line, the parameters to the function should be suppliedas command line arguments. For example, for the following function header of a program in thefile text.txt:function main a: integer, b: integer returns integer;One would execute the program as follows:$ ./compile < test.txt 2 4In this case, the parameter a would be initialized to 2 and the parameter b to 4.An example of a program execution is shown below:$ ./compile < test.txt 2 41 function main a: integer, b: integer returns integer;2 c: integer is3 if a > b then4 a rem b;5 else6 a ** 2;7 endif;8 begin9 case a is10 when 1 => c;11 when 2 => (a + b / 2 – 4) * 3;12 others => 4;13 endcase;14 end;Compiled SuccessfullyResult = 0After the compilation listing is output, the value of the expression which comprises the body ofthe function should be displayed as shown above.The existing code evaluates some of the arithmetic, relational and logical operators together withthe reduction statement and integer literals only. You are to add the necessary code to include allof the following: Real and Boolean literals All additional arithmetic operators All additional relational and logical operators Both if and case statements Functions with multiple variables Functions with parametersThis project requires modification to the bison input file, so that it defines the additional thenecessary computations for the above added features. You will need to add functions to thelibrary of evaluation functions already provided in values.cc. You must also make somemodifications to the functions already provided.You are to submit two files.1. The first is a .zip file that contains all the source code for the project. The .zip fileshould contain the flex input file, which should be a .l file, the bison file, which shouldbe a .y file, all .cc and .h files and a makefile that builds the project.2. The second is a Word document (PDF or RTF is also acceptable) that contains thedocumentation for the project, which should include the following:a. A discussion of how you approached the projectb. A test plan that includes test cases that you have created indicating what aspectsof the program each one is testing and a screen shot of your compiler run on thattest casec. A discussion of lessons learned from the project and any improvements that couldbe made CMSC 430 Project 3
The third project involves modifying the attached interpreter so that it interprets programs for the
complete language.
You may convert all values to double values, although you can maintain their individual types if
you wish.
When the program is run on the command line, the parameters to the function should be supplied
as command line arguments. For example, for the following function header of a program in the
file text.txt:
function main a: integer, b: integer returns integer;
One would execute the program as follows:
$ ./compile < test.txt 2 4 In this case, the parameter a would be initialized to 2 and the parameter b to 4. An example of a program execution is shown below: $ ./compile < test.txt 2 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 function main a: integer, b: integer returns integer; c: integer is if a > b then
a rem b;
else
a ** 2;
endif;
begin
case a is
when 1 => c;
when 2 => (a + b / 2 – 4) * 3;
others => 4;
endcase;
end;
Compiled Successfully
Result = 0
After the compilation listing is output, the value of the expression which comprises the body of
the function should be displayed as shown above.
The existing code evaluates some of the arithmetic, relational and logical operators together with
the reduction statement and integer literals only. You are to add the necessary code to include all
of the following:






Real and Boolean literals
All additional arithmetic operators
All additional relational and logical operators
Both if and case statements
Functions with multiple variables
Functions with parameters
This project requires modification to the bison input file, so that it defines the additional the
necessary computations for the above added features. You will need to add functions to the
library of evaluation functions already provided in values.cc. You must also make some
modifications to the functions already provided.
You are to submit two files.
1. The first is a .zip file that contains all the source code for the project. The .zip file
should contain the flex input file, which should be a .l file, the bison file, which should
be a .y file, all .cc and .h files and a makefile that builds the project.
2. The second is a Word document (PDF or RTF is also acceptable) that contains the
documentation for the project, which should include the following:
a. A discussion of how you approached the project
b. A test plan that includes test cases that you have created indicating what aspects
of the program each one is testing and a screen shot of your compiler run on that
test case
c. A discussion of lessons learned from the project and any improvements that could
be made
Here is the approach I recommend for project 3.
1) Study the skeleton project provided, built it and run it so that you understand how semantic
actions are used to perform the evaluation needed to interpret programs in our language.
2) You should incorporate the new features that are in the skeleton into your version of project 2
and be sure that it builds and runs just as the skeleton did. Then confirm that test cases
test1.txt – test4.txt that were provided as test cases for the skeleton code produce the
correct output. Note that changes are required to both parser.y and scanner.l.
3) Make additions as defined by the specification incrementally. Start with adding the literals of
the real and Boolean data types. These changes involve modifications to scanner.l. . Once you
have made these modifications use test5.txt and test6.txt to test them. Shown below is the
output that should result when using both test cases as input:
$ ./compile < test5.txt 1 2 3 4 5 6 -- Function with arithmetic expression using real literals function main returns real; begin 8.3e+2 + 2.E-1 * (4.3E2 + 2.8) * 3.; end; Compiled Successfully Result = 1089.68 $ ./compile < test6.txt 1 2 3 4 5 6 7 // Function containing Boolean literals function main returns boolean; begin true and false; end; Compiled Successfully Result = 0 4) Next, add the necessary semantic actions for each of the new arithmetic operators. Create individual test cases to test each new operator. Once you have verified that the operators are evaluated correctly in those cases, use test7.txt, which will test all of them along with their precedence. Shown below is the output that should result when using that test case as input: $ ./compile < test7.txt 1 2 3 // Arithmetic operators function main returns integer; 4 5 6 begin 9 + 2 - (5 - 1) / 2 rem 3 * 3 ** 1 ** 2; end; Compiled Successfully Result = 5 5). Do the relational operators next. As before it is a good idea to create individual test cases to test each new operator. Finally the two logical operators or and not testing each with separate test cases. Once you have added all the new operators use test8.txt to test them. Shown below is the output that should result when using that test case as input: $ ./compile < test8.txt 1 -- Relational and logical operators 2 3 function main returns boolean; 4 begin 5 (5 + 3 > 8 or 9 / 3 = 3) or (7 – 9 < 1) and (not (3 /= 1 * 7) or 6 = 9); 6 end; Compiled Successfully Result = 1 6) The if statement would be a good next step. It can be done in one line using the conditional expression operator. Use test9.txt to test it. Shown below is the output that should result when using that test case as input: $ ./compile < test9.txt 1 2 3 4 5 6 7 8 9 10 -- Conditional expression function main returns integer; begin if not (5 + 4 >= 9) then
6 + 9 * 3;
else
8 – 9 rem 7;
endif;
end;
Compiled Successfully
Result = 6
7) Do multiple variable declarations next. Use test10.txt and test11.txt to test that change.
Shown below is the output that should result when using both test cases as input:
$ ./compile < test10.txt 1 2 3 4 5 6 7 8 -- Multiple integer variable initialization function main returns integer; b: integer is 5 + 1 - 4; c: integer is 2 + 3; begin b + 1 - c; end; Compiled Successfully Result = -2 $ ./compile < test11.txt 1 2 3 4 5 6 7 8 9 10 11 12 -- Variable initialization with real and Boolean variables function main returns real; b: real is 5.3 + 1. - 4 / 2.0E-2; c: boolean is b > 3.e2 and true or false;
begin
if c then
b * 6.4 + 1.5;
else
2.e+3;
endif;
end;
Compiled Successfully
Result = 2000
8) Next make the changes necessary for programs that contain parameters. The parameters are in
the command line arguments, argv. The prototoype of main is:
int main(int argc, char *argv[])
Declare a global array, which is dynamically allocated based on argc, at the top of parser.y. In
main convert each command line argument to a double and store it into that global array. The
function atof will do the conversion of a char* to a double. In the semantic action for the
parameter production, retrieve the value of the corresponding parameter from the global array
and store its value in the symbol table.
Use test12.txt and test13.txt to test that change. Shown below is the output that should
result when using both test cases as input:
$ ./compile < test12.txt 3.6 1 2 3 4 5 -- Single parameter declaration function main a: real returns real; begin a + 1.5; 6 end; Compiled Successfully Result = 5.1 $ ./compile < test13.txt 1 8.3 1 2 3 4 5 6 7 8 9 10 -- Two parameter declarations function main a: boolean, b: real returns real; begin if a then b + 1; else b - 1; endif; end; Compiled Successfully Result = 9.3 9) Save the case statement for last. It is the most challenging. The approach that I recommend is using an inherited attribute. Study how an inherited attribute is used in the skeleton for the reductions. A similar approach can be used with the case statement. Here is pseudo-code for semantic actions for handling the case statement. It uses the sentinel NAN, not-a-number as the attribute carried up the parse tree to indicate a match has not yet been found. In that way, the decision can be made at the top level when the value of the case should be what is in the OTHERS clause: statement: CASE expression IS cases OTHERS ARROW statement_ ENDCASE {If the attribute of cases, is a number then return it as the attribute otherwise return the attribute of the OTHERS clause}; cases: cases case {if the attribute of cases is a number then return it as the attribute otherwise return the attribute of case} | %empty {Set the attribute to the sentinel NAN} ; case: WHEN INT_LITERAL ARROW statement_ {$-2 contains the value of the expression after CASE. It must be compared with the attribute of INT_LITERAL. If they match the attribute of this production should become the attribute of statement_ If they don't match, the attribute should be set to the sentinel value NAN} ; NAN is a constant defined in cmath that represents not-a-number. The function isnan checks whether a double is NAN. Use test14.txt to test the case statement. . Shown below is the output that should result when using that test case as input: $ ./compile < test14.txt 1 2 3 4 5 6 7 8 9 10 11 // Case selection function main returns integer; a: integer is 4 + 2; begin case a is when 1 => 3;
when 2 => (3 + 5 – 5 – 4) * 2;
others => 4;
endcase;
end;
Compiled Successfully
Result = 4
10) The final two test cases, test15.txt and test.16.txt, involve nested statements and
provide a further test of both the if and case statements. Shown below is the output that should
result when using both test cases as input:
$ ./compile < test15.txt 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 -- Nested if function main a: integer returns integer; b: integer is 8; begin if a >= 0 then
if b > 5 then
a * 2;
else
a + 5;
endif;
else
a / 2;
endif;
end;
Compiled Successfully
Result = 2
$ ./compile < test16.txt 3 1 1 2 -- Nested case 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 function main a: integer, b: integer returns integer; c: integer is 8; begin case a is when 1 => a * c;
when 2 => a + 5;
when 3 =>
case b is
when 1 => 2;
others => 19;
endcase;
when 4 => a / 2;
others => a + 4;
endcase;
end;
Compiled Successfully
Result = 2
All of the test cases discussed above are included in the attached .zip file.
You are certainly encouraged to create any other test cases that you wish to incorporate in your
test plan. Keep in mind that your compiler should produce the correct output for all syntactically
correct programs, so I recommend that you choose some different test cases as a part of your test
plan. I may use a comparable but different set of test cases when I test your projects.