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| #include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
/**
* Types definitions
*/
/**
* \enum bool_t
* \brief A boolean value is either true or false
*/
typedef enum bool_e {false, true} bool_t;
/**
* \struct : token_t
* \brief It represents a tokens : either an operator or an number
*/
typedef struct token_t {
union {
long nb; /*!< A number */
char op; /*!< An operator */
} token;
int type; /*!< Token type 0 = digit, 1 = operator */
} token_t;
/**
* \struct : token_list_t
* \brief A list of token is a /token/ and a pointer to the /next/ element of the list.
*/
typedef struct token_list_s {
token_t token; /*!< A token */
struct token_list_s * next; /*!< A pointer to the next token */
} token_list_t;
/**
* \struct : token_queue_t
* \brief A queue holds the head /hd/ and the tail /tl/ of the list
*/
typedef struct token_queue_s {
struct token_list_s * hd; /*!< A pointer to head of the queue */
struct token_list_s * tl; /*!< A pointer to tail of the queue */
} token_queue_t;
/**
* \struct : token_tree_t
* \brief A tree of tokens is a /token/ and two pointers toward its chidrens
*/
typedef struct token_tree_s {
token_t token; /*!< A token */
struct token_tree_s * left; /*!< A pointer to the left child */
struct token_tree_s * right; /*!< A pointer to the right child */
} token_tree_t;
/**
* List Implementation
*/
/**
* \fn cons
* \brief conses an element to the list
*
* @param token : token_t
* @param list : token_list_t
* @return A pointer to the head of the list : token_list_t *
*/
token_list_t *
cons (token_t token, token_list_t * list) {
token_list_t * elem = NULL;
if ((elem = malloc(sizeof *elem)) == NULL) {
perror("cons");
return NULL;
}
elem->token = token;
elem->next = list;
return elem;
}
/**
* \fn free_token_list
* \brief frees the list of tokens /list/
*
* @param list : token_list_t
*/
void
free_token_list (token_list_t * list) {
while (list != NULL) {
token_list_t * current = list;
list = list->next;
free(current), current = NULL;
}
}
/**
* FIFO implementation
*/
/**
* \fn token_list_init
* \brief Initializes a queue of tokens
*
* @return A pointer to the queue : token_queue_t *
*/
token_queue_t *
token_queue_init (void) {
token_queue_t * queue = NULL;
if ((queue = malloc(sizeof *queue)) == NULL) {
perror("malloc");
return NULL;
}
queue->hd = queue->tl = NULL;
return queue;
}
/**
* \fn token_queue_is_empty
* \brief Checks if the /queue/ is empty
*
* @param queue : token_queue_t
* @return true if empty, otherwize false
*/
bool_t
token_queue_is_empty (token_queue_t * queue) {
return queue->tl == NULL;
}
/**
* \fn token_queue_push
* \brief Pushes an element /token/ on the back of the tokens' queue /queue/
*
* @param token : token_t
* @param queue : token_queue_t *
* @return true is success, otherwize false : bool_t
*/
bool_t
token_queue_push (token_t token, token_queue_t * queue) {
token_list_t * elem = NULL;
if ((elem = cons(token, NULL)) == NULL) {
perror("token_queue_push");
return false;
}
if (token_queue_is_empty(queue))
queue->hd = elem;
else
queue->tl->next = elem;
queue->tl = elem;
return true;
}
/**
* \fn token_queue_pop
* \brief Pops an element
*
* @param queue : token_queue_t *
* @param elem : token_t *
* @return true is success, otherwize false : bool_t
*/
bool_t
token_queue_pop (token_queue_t * queue, token_t * elem) {
token_list_t * cel;
if ((cel = queue->hd) == NULL) {
perror("token_queue_pop");
return false;
}
*elem = cel->token;
if ((queue->hd = cel->next) == NULL)
queue->tl = NULL;
free(cel), cel = NULL;
return true;
}
/**
* \fn token_queue_free
* \brief Frees a queue of tokens
*
* @param queue : token_queue_t *
*/
void
free_token_queue (token_queue_t * queue) {
free_token_list(queue->hd);
free(queue);
}
/**
* \fn token_tree_init
* \brief Initializes a tree of tokens
*
* @return A pointer to a tree of tokens
*/
token_tree_t *
token_tree_init (void) {
token_tree_t * tree = NULL;
if ((tree = malloc(sizeof *tree)) == NULL) {
perror("malloc");
return NULL;
}
tree->left = tree->right = NULL;
return tree;
}
/**
* Lexical analysis
*/
/**
* \fn is_operator
* \brief Checks if /c/ is an operator
*
* @param c : unsigned int
* @return true if /c/ is an operatoir, otherwize false : bool_t
*/
bool_t
is_operator(unsigned int c) {
return c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == ')';
}
/**
* \fn is_token
* \brief Checks if /c/ is a token
*
* @param c : unsigned int
* @return true if /c/ is a token, otherwize false : bool_t
*/
bool_t
is_token (unsigned int c) {
return isdigit(c) || is_operator(c);
}
/**
* \fn read_token
* \brief Reads a token and returns it
*
* @param stream : char **
* @return The read token : token
*/
token_t
read_token (char ** stream) {
token_t t;
while (isspace(**stream))
(*stream)++;
if (is_token((unsigned int)**stream)) {
if (isdigit((unsigned int)**stream)) {
t.token.nb = strtol(*stream, stream, 10);
t.type = 0; /* 0 = digit */
} else {
t.token.op = **stream;
t.type = 1; /* 1 = operator */
(*stream)++;
}
}
return t;
}
/**
* \fn tokenize
* \brief This function divides the stream in a list of tokens
*
* @param stream : char *
* @return A pointer to the list of tokens : token_queue_t *
*/
token_queue_t *
tokenize (char * stream) {
token_queue_t * tokens, token_tree * ast = NULL;
token_t gardien;
tokens = token_queue_init();
while (*stream)
token_queue_push(read_token(&stream), tokens);
/* And the gardien */
gardien.type = 1;
gardien.token.op = '\0';
token_queue_push(gardien, tokens);
return tokens;
}
/**
* Syntax analysis
*/
/**
* \fn syntax_error
* \brief prints a syntax error
*
* @param f_tkn : const token_t
* @param msg : const char *
*/
void
syntax_error (const token_t f_tkn, const char * msg) {
if (!f_tkn.type) /* digits */
fprintf(stderr, "Syntax error : '%d' found. %s", current.token.nb, msg);
else /* operators */
fprintf(stderr, "Syntax error : '%c' found. %s", current.token.op, msg);
}
token_tree_t * /* Must be able to catch epsilon | nullifiable */
_expr (token_queue_t * tokens, token_tree * ast) {
token_t current = tokens->hd->token;
if (current.type == 1) {
if (current.token.op == '+' || current.token.op == '-')
/* ajoute jeton */;
term();
_expr();
else if (current.token.op == ')')
/* End */
} else {
syntax_error(current, "An operator is expected.");
}
}
token_tree_t * /* Must be able to catch epsilon | nullifiable */
_term (token_queue_t * tokens, token_tree * ast) {
token_t current = tokens->hd->token;
if (current.type == 1) {
if (current.token.op == '*' || current.token.op == '/')
/* ajoute jeton */;
factor();
_expr();
else if (current.token.op == ')')
/* End -> return NULL */
} else {
syntax_error(current, "An operator is expected.");
}
}
token_tree_t *
factor (token_queue_t * tokens, token_tree * ast) {
token_t current = tokens->hd->token;
if (current.type == 0) { /* digits */
/* ajoute (digits); */
} else if (current.type == 1 && current.token.op == '(') {
expr(tokens);
} else {
syntax_error(current, "Number or opening brace is expected.");
}
}
token_tree_t *
term (token_queue_t * tokens, token_tree * ast) {
token_t current = tokens->hd->token;
if (current.type == 0) { /* digits */
factor(tokens);
_term(tokens);
} else if (current.type == 1 && current.token.op == '(') {
factor(tokens);
_term(tokens);
} else {
syntax_error(current, "Number or opening brace is expected.");
}
}
token_tree_t *
expr (token_queue_t * tokens, token_tree * ast) {
token_t current = tokens->hd->token;
if (current.type == 0) { /* digits */
term(tokens);
_expr(tokens);
} else if (current.type == 1 && current.token.op == '(') {
term(tokens);
_expr(tokens);
} else {
syntax_error(current, "Number or opening brace is expected.");
}
}
/**
* \fn parse
* \brief Use a list of /tokens/ to make an abstract syntax tree
*
* @param tokens : token_queue_t *
* @return An abstract syntax tree : token_tree_t *
*/
token_tree_t *
parse (token_queue_t * tokens) {
return expr(tokens);
}
/**
* \fn eval
* \brief This function evaluates a mathematical expression and returns the result of this one
*
* @param expr : char *
* @return The result of the mathematical expression : long
*/
long
eval (char * expr) {
long result = 0;
token_queue_t * tokens;
token_tree_t * ast;
tokens = tokenize(expr);
ast = parse(tokens);
/*result = compute_ast(ast);*/
free_token_queue(tokens), tokens = NULL;
return result;
}
int
main (void) {
char expression[] = "0-2*((2+3)*(2-3))/5"; /* = 2 */
printf("%d", eval(expression));
return EXIT_SUCCESS;
} |
Construction d'un arbre syntaxique abstrait
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