Java代写 | 编译原理 UNIQUEID HW1


Instructions: Submit to Canvas a single zip file that contains an electronic copy of your answers and programs. The zip file must have the following directory structure, where uniqueid is qwer:
uniqueidHW1 uniqueidHW1.pdf
top-level directory containing all of your stuff
; which contains the output for exercise (1) and report for exercise (2) directory containing your source code for exercise (2)
main.cpp, helper.cpp, etc ; your source code in either C++ or Java,, etc ; please, do not put your code into packages
For instance, if your uniqueid were inclezd and your solution for exercise (2) were written in Java, your zip file should contain the following directory structure:
inclezdHW1 inclezdHW1.pdf
inclezdL,, etc.
Make sure that your main file is called either or main.cpp, depending on the language you used for the implementation. No other file names are allowed for the main file.
(2). (90/90) Consider a simple programming language named L. The L programming language has the following features:
● L variables can store a string, a Boolean, or an integer value. A single variable can switch between string, Boolean, and integer values during program execution. Assigning a value to a variable creates that variable for future use. A runtime error occurs if a variable is used before it is given a value. Boolean values are denoted by the reserved words TRUE and FALSE.
● Variables are case sensitive and consist only of upper and lower-case letters.
● The following are L reserved words: PRINT, FOR, TRUE, FALSE, WHILE, DO, LESSTHAN
plus the reserved symbols { and }.
LESSTHAN, WHILE, and DO are only relevant for graduate students.
● You may assume that any L program given as an input to your interpreter is syntactically correct.
● The PRINT statement should display one variable’s value. Here is an example of a PRINT statement in
language L:
PRINT apples ;
If cookies is an integer variable with value 4, the output of your interpreter should be:
If cookies is a Boolean variable with value TRUE, the output of your interpreter should be: 1

If cookies is a string variable with value “red delicious”, the output should be:
apples=”red delicious”
● The left-hand side of an assignment statement (i.e., =) is a variable.
● The right-hand side of a simple assignment statement (i.e., =) is either a variable name, a signed integer, string literal, or the Boolean values TRUE or FALSE. If the right-hand side of the assignment is a variable, then this variable must already have a value; otherwise the assignment should trigger a runtime error to be reported by your interpreter. For example, the following are valid assignments:
A = 12 ; A=B;
A = “hello” ; A = “12” ;
A = TRUE ;
The following is not a valid assignment, assuming C has no value yet:
● There are three compound assignment statements: +=, *=, and &=. The meaning of these operators depends on the data type of the left and right-hand side of the operator.
<string var> += <string>
<integer var> += <integer>
<integer var> *= <integer>
<Boolean var> &= <Boolean>
concat right string onto end of left string
increment left integer with value on right
multiply left integer by value on right
assign to left Boolean the result of performing
a Boolean AND operation between values on left
and right
A=4; A += 34 ; A *= B ;
C = “t” ;
C += “hello world” ;
D &= TRUE ;
All other combinations (e.g., += with string var on the left and integer on the right) are illegal and should cause a runtime error.
● Every statement is terminated by a semi-colon.

● L programs must have at least one space separating all lexical elements.
● There is a for loop statement – FOR – whose body contains at least one simple statement (i.e., at least one assignment), which is presented on one line. The keyword FOR is followed by an integer constant, which indicates the number of times to execute the loop. Following this number is the reserved symbol { followed by a sequence of statements defining the loop’s body and ending with the reserved symbol }, as done here:
FOR 5 { B += A ; A *= 2 ; }
● L for loops can be nested and must appear on one line:
FOR 5 { B += A ; A *= 2 ; FOR 10 { A += B ; } A += 2 ; }
● Here is an example L program:
FOR 5 { B += A ; A *= 2 ; } A += 1000 ;
This program’s output is:
A=1032 B=31
As an example, an equivalent Python program would be (Do not translate L code into Python!):
for i in range(5):
B += A
A *= 2 A += 1000
print(“A=” + str(A))
print(“B=” + str(B))
Here is a second L program:
A = 10 ;
A += A ;
A = “hello” ;
A += A ;
A += 123 ;

The output to this second program would yield an error. Your program should display the line number of this error and then stop processing:
● You may assume that the programs are syntactically correct but may have runtime errors (e.g., add integer and string, use a variable without a value on the right-hand side of an assignment, etc.).
Tasks and scoring:

(80/80 points) Write an interpreter (Java or C++) to execute L programs o (30/10 points) Basic structure, integer variables only
o (25/25 points) Basic structure, integer, plus string and Boolean variables o (10/5 points) For loops
o (10/20 points) Nested for loops
o (5/5 points) Detection of runtime errors
(10/10 points) Write a report that:
o Explicitly states what works in your interpreter and what does not.
o Provides the output of your interpreter when run on the sample L programs provided in the
“Sample” archive in Canvas.
o Compares the runtime speed of L programs versus an equivalent program in some compiled
language (e.g., C++). Provide timings to support your estimate. Are your findings typical of interpreted languages? Describe how you set up the experiment in order to obtain meaningful timings (e.g., what L programs you used for testing – note that you can write your own L programs).


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