Automated C++ Program Generator using English Language Interface

Transcription

1 Automated C++ Program Generator using English Language Interface Ambuj Kumar and Prof. (Mrs.) Saroj Kaushik Department of Computer Science & Engineering Indian Institute of Technology, Delhi Hauz Khas, New Delhi India Abstract Automatic Programming is an ability of a computer to develop a program all by itself, once the problem has been stated in some specified domain using some suitable format [2]. We have developed automated C++ program generator which takes an input in English and generate C++ program. Once a problem has been specified in English, the system is able to interpret it and generate a C++ program using its knowledge base, inference engine as well as some intelligence. The domain of programs to be generated is data structures such as sorting, searching, linked lists, file handling, manipulating strings, numbers etc. The system has been implemented using Java in Linux environment. Keywords: Automatic Programming, analyzer, classifier, program generator, database of algorithms, processing of English text. 1. Introduction Automatic Programming has been a goal of computer science and artificial intelligence since the first programmer came face to face with the difficulties of programming [1]. The first automated programs were assemblers and compilers, developed in 1950's. Today, they are not considered as automated programs. However, these were invented at a time when most of the programming was done in machine language. Assemblers represented a spectacular level of automation compared with programming in machine code. Automatic Programming may be considered as an ability of a computer to generate programs automatically where the problem is specified in some suitable format [2]. Of course, there is no doubt that automated Programming will be domain specific. MIT (USA) is working on a similar concept. They have named their software as METAPHOR. It understands description of objects and generate templates of classes and functions accordingly [3]. For example, if we provide a description as An animal has 4 legs and 1 tail. A cow is an animal, then, METAPHOR software is able to generate a code as follows :- class animal { private : int legs, tail; public: }; animal() { legs = 4; tail = 1; } class cow : public animal{ }; cow(); The proposed system is currently able to interpret problems stated in English related to strings, numbers, linked lists and file handling 1

2 and generate full C++ program which could be run straight way. So, our system is different from METAPHOR. Instead of generating class definitions, it focuses directly on complete program generation. It has inference engine and makes use of knowledge base of templates of various programs. It is possible to extend the knowledge base and inference engine capability of this tool to make it even more powerful. Currently supported operations are listed in Appendix. 2. Architecture of System Overall architecture of the system is shown in fig.1. It mainly consists of input module, database of program skeletons, dictionary and program generator module. 2.1 Input Module It consists of Analyzer and classifier. The analyzer takes the problem statement given by the user in English. Basically, it creates a list of all meaningful words present in the problem statement and ignores irrelevant or noise words. The dictionary of meaningful words is maintained. It also performs spell check and reports suspected mistakes, if any. The user can then suggest suitable replacements. The classifier reads all the words present in the word list and interprets the meaning of user input. It identifies the type of problem and reports an error, if unable to interpret input statement of the problem Database of Algorithms The database of algorithms is maintained for string handling, number manipulation, arrays, linked lists (stack, queues, dequeues), sorting and file handling. The prototype of algorithms is stored and used to generate C++ program which may contain combination of more than one algorithm Program generator This is the most important part of the system. It generates the program on the basis of the problem's type decided by the classifier. The program generator goes through the word list generated by the analyzer, and hence decides which algorithms to use Processing of English text The word Natural Language Processing implies that we should be able to interpret the meaning of a statement even if it is specified in several different ways. This can be illustrated by the following example with reference to our system. Suppose we want to do the following sequence of operations. We create a singly linked list. Insert some nodes in it. Delete some nodes from it. Sort the list. Reverse the list. Finally, display the original list. This sequence of steps can be specified as a problem statement in several ways as illustrated below. Create a linked list, insert 5 elements into it, delete 4 elements, sort it, reverse it and then display the original list. Here, system can not infer the type of linked list one wants to create. So, it will prompt user to choose amongst different types of linked lists available, such as singly linked, doubly linked, circular singly linked lists etc. Further, the type of data is not specified in the statement. So, the user will be prompted to specify the type of elements in the list. Sorting of list will be done on the basis of some field which is not clear from the statement. The user will be asked to specify that too. Here original list may refer to the one created as linked list or the sorted one. User will identify which one he is interested and correspondingly that list will be preserved for displaying purpose. If input texts are as follows: Write a program which creates a singly linked list of integer values, put 5 elements into it, remove 4 elements from it, sort the list using insertion sort method, then invert the list and finally displays the sorted list. Here system will not ask above mentioned questions and will simply generate desired code. In this way, there can be several different ways of specifying the same problem statement, but all will have the same interpretations as illustrated above. The analyzer creates a list of meaningful words and irrelevant words are ignored. Let us consider an example, please generate for me a code for sorting an array of strings. The analyzer creates a word list sort, array and 2

3 strings. Other words are totally irrelevant and hence are ignored. On the basis of the word strings, the system decides that this is a problem of string handling. From the word array, the system judges that there will be multiple inputs, and hence asks for an array size. The word sort forces the system to ask for sorting algorithm to be used. Once all these information have been received, the system fits various algorithm programs using appropriate templates. For detailed working of the software refer to Appendix1. 3. Implementations The Dictionary has been implemented as a hashed file which contains all the relevant and meaningful words along with synonym words such as string and text are synonyms in the context of programming. When the system is started, then an adjacency list is created after scanning the entire dictionary file system. The adjacency list corresponding to a word contains all its synonyms. This adjacency list is used to comprehend the words each time a new question is given to the system. The repository of algorithms is nothing but a list of files, each file containing the skeleton of C++ code for the algorithm. The template data type of C++ has been used in many of these codes. The operations supported by the system are given below. The combinations of operations are also permitted. The details of directory structure of the system are shown in appendix1. Appendix 2 contains explanation and use of the system. Various programs generated using this system are included in appendix3. Operations on strings: concatenation, string comparison, substring checks, sorting (ascending /descending order) using different algorithms, conversion to upper/lower case, string reversal palindrome check, alphabetically first/last string from a set of strings (For examples, user may ask system to generate program for sort the string and reverse it and then concatenate with another string ) Operations on numbers: check for prime numbers, palindrome numbers, Fibonacci numbers, even/odd numbers, reversing digits of a number, sorting (ascending/descending order) using different algorithms, statistical operations such as maximum, minimum, average, standard deviation and variance (For example, write program for checking a given number whether it is palindrome and prime both ) Operations on linked lists: singly linked list, singly circular linked list, doubly linked list, doubly circular linked list, stack, queue, deques (using array or linked list concept), generalized linked list. Here the node structure of list is generalized one. Operations on files: A very generalized code is created to add/delete/search records in a file. (The structure of records is generalized.) 3.1. Proposed algorithm for generating C++ program The algorithm used in the proposed system is given below: Step 1: Read the query (problem statement in English) from the user. Step 2: Break up the problem statement into a list of words. Step 3: For each word in list do { if word key_list, retain it else if word ignore_list, remove it else suggest suitable correction using well known LCS algorithm /*this is a case of misspelled word*/ and goto Step3 & continue from this word. } Step 4: Analyze the filtered list of words obtained from above step. If the list is sufficient to comprehend the problem, goto Step 5 else give an error message and exit. Step 5: Depending on the sequence in which the words occur in the list generated after Step 3, generate the program and fit the function templates using the directory./ knowledge / algorithms in proper places Platform and Environment used The system is implemented on Linux environment using JAVA as we mainly require string processing. JAVA has a vast number of functions for the same (provided by the classes String and StringBuffer), which enable us to write very short codes for practically any type of string handling operations. Further, we need to handle the adjacency list of words. This is also done using the Vector class provided by java.util package. 3

4 Figure 1: Architecture of the system 4. Conclusion This system is currently able to generate simple programs similar to the level of programming taught in first year of undergraduate. But, this is not the end of it. It is not merely an academic exercise in futility. This software has a lot of growth potential. Of course, this software is domain specific. But, it can be extended to generate algorithms (functions or templates) on the basis of a process description given to it. In other words, it is possible to extend its inference engine so that it can comprehend English sentences, and come up with a logical analysis of the process being described. References [1] Charles Rich, Richard C. Waters. Approaches to Automatic Programming, Mitsubishi Electric Research Laboratory Technical Report, July [2] Charles Rich and Richard C. Waters Automatic programming: Myths and prospects IEEE Computer, 21(8):40-51, August [3] Daniel C. Halbert, Watch What I Do: Programming by Demonstration, chapter SmallStar: Programming by Demonstration in the Desktop Metaphor, pp , MIT Press, Cambridge, MA,

5 Appendix 1 Detailed working of the software Here is the directory structure of the system is shown in the figure below. The directories are explained as follows: src directory containing the JAVA source codes. classes.class files generated after compilation. doc documentation directory. shell contains the shell scripts being used internally to control the working of the software. These shell scripts are embedded within the software to handle simple issues such as executing the auto-generated C++ programs. knowledge contains 3 files namely word_list, key and ignore called knowledge base files. The file key contains the list of keywords i.e. those words which are critical for the purpose of understanding the meaning of a sentence. The file ignore contains a list of commonly occurring words which have no significance in the context of understanding of the programming problem statement e.g. words like is, are, the etc. The file word_list contains {key ignore (synonyms of words present in key)}. It contains two more directories dictionary - the storehouse of all words which are understood by this system along with links to corresponding synonyms of word if they exist. algorithms - contains generalized C++ templates for some standard functions. Figure 2: File structure of the software Startup phase The following sequence of steps is executed only once, i.e. when we start our system for the first time. This phase is particularly concerned with creation of adjacency list of words. The startup algorithm is described below which is followed Appendix 2 by main algorithm described in sub section 3.2. for all words in word_list do { - open file with the same name as the word (file is present in./dictionary) - add all words in file (except the word itself) to the adjacency list of the word } We feel that the reader still may not be able to fully understand what sort of natural language 5

6 processing is going on in the system discussed above. It may just appear like a keyword-based code fitting system. Obviously, a knowledge base of standard algorithms has to be present in some form or the other in such type of systems. The intelligence and natural language processing primarily deal with proper utilization of this knowledge base along with following some common-sense rules. So, we present a simple example to look at these issues. If the user s statement is Read N integers, sort them, then determine if the original list of integers are palindrome. Also, check if they are prime. Prima facie, it seems that the program construction will follow the following sequence of steps but, this is not exactly what happens. i. It will declare necessary variables to input N integers i.e. it will just declare an array. ii. Then, it will fit the code to take input from the user. iii. Finally, it will just fit the codes to sort the array, palindrome and prime numbers checks. The performance is obviously restricted by the size of knowledge base and available inference rules. However, it is possible to scale this system to any desired extent. As far as the contribution to software development is concerned, we all know that there are certain algorithms/code fragments which are needed again and again, but in various forms. For example, different types of linked lists are frequently used. But a major bottleneck is different structure of the node for different applications. This significantly increases the work involved. Using our system, a lot of time can be saved as far as generating a basic implementation of linked list is concerned. Any datatype can be incorporated in it. All the basic functions will also be generated. So, the programmer can customize the code to suit his needs within a few minutes. Simple features like the one described above will certainly help save at least a few hours of coding time. The steps (i) and (ii) described above are true, but step (iii) has some finer aspects to it. We have not specified whether it is an ascending order sort or descending order sort. By default, the system assumes it to be ascending order. Have a look at 2 keywords then and original sequence. These words may appear irrelevant to code generation, but the real picture is not so. The keyword then determines that the check for palindrome has to be done strictly after sorting. There is another catch to it. It says that check for palindrome has to be done only on the original sequence of input and NOT on the sorted sequence. Further, the ambiguity lies in which sequence to check for primality. So, we let the system ask the user whether he wants to do primality testing on original list or sorted list. This is done as soon as the problem is analyzed by the system. Here lies the intelligence. If the system is unable to decide what to do, it either asks the user or takes a default action (as in case of sorting). Practical feasibility of the system 6

7 Appendix 3 We will present snapshots of various examples. Example 1: Do the Sorting on an array of numbers, checking if they are prime and then finding their mean. The program generated as follows: Figure 3: The query window for Example 1 Figure 4: The response to the query 7

8 Example 2: Implement a doubly linked list Figure 5: The query for a linked list operation The program generated as follows: Figure 6: Asking for the elements of the node Figure 7: The response to the query 8

9 Example 3: Operations on record based files Figure 8: The query for a general filesystem The program generated as follows: Figure 9: Asking for the fields of record Figure 10: The response to the query 9

10 Example 4: Sort N strings, reverse them, find their lengths and then convert each of them to upper case Figure 11: A query for operations on strings Figure 12: Asking for the sorting algorithm Figure 13: Asking for number of strings Figure 14: The response to the query 10