我已经将//---- tokenize.h ----
#define TERMINAL 0
#define OPERAND 1
#define ERROR 2
#define ADD '+'
#define SUBTRACT '-'
#define MULTIPLY '*'
#define DIVIDE '/'
#define EXPONENT '^'
#define L_PARENTHESIS '('
#define R_PARENTHESIS ')'
#define SYNTAX_ERROR 1
#define PAREN_ERROR 2
typedef struct context {
char *p;
char *nextp;
int parenthesis_balance;
int error_code;
double value;
} context;
int this_token(context *cp);
void skip_token(context *cp);
//---- tokenize.c ----
#include <stdlib.h>
//#include "tokenize.h"
int this_token(context *cp) {
char *p = cp->p;
for (;;) {
switch (*p) {
case '\0':
cp->nextp = p;
return TERMINAL;
case ' ':
case '\t':
case '\n':
/* ignore white space */
p++;
continue;
case ADD:
case SUBTRACT:
case MULTIPLY:
case DIVIDE:
case EXPONENT:
case L_PARENTHESIS:
case R_PARENTHESIS:
/* single character operators */
cp->nextp = p + 1;
return *p;
default:
/* try and parse as a number constant */
cp->value = strtod(p, &cp->nextp);
if (cp->nextp > p)
return OPERAND;
return ERROR;
}
}
}
void skip_token(context *cp) {
cp->p = cp->nextp;
}
//---- parse.h ----
int parse(char expression[], double *result);
void solve(char expression[]);
//---- parse.c ----
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
//#include "tokenize.h"
//#include "parse.h"
/* expression parsers return non zero upon error */
int try_add_sub(context *cp, double *result);
int try_mul_div(context *cp, double *result);
int try_exp(context *cp, double *result);
int try_primary(context *cp, double *result);
int try_add_sub(context *cp, double *result) {
if (try_mul_div(cp, result))
return 1;
for (;;) {
double operand;
switch (this_token(cp)) {
case ADD:
skip_token(cp);
if (try_mul_div(cp, &operand))
return 1;
*result += operand;
continue;
case SUBTRACT:
skip_token(cp);
if (try_mul_div(cp, &operand))
return 1;
*result -= operand;
continue;
}
return 0;
}
}
int try_mul_div(context *cp, double *result) {
if (try_exp(cp, result))
return 1;
for (;;) {
double operand;
switch (this_token(cp)) {
case MULTIPLY:
skip_token(cp);
if (try_exp(cp, &operand))
return 1;
*result *= operand;
continue;
case DIVIDE:
skip_token(cp);
if (try_exp(cp, &operand))
return 1;
*result /= operand;
continue;
}
return 0;
}
}
int try_exp(context *cp, double *result) {
if (try_primary(cp, result))
return 1;
if (this_token(cp) == EXPONENT) {
double operand;
skip_token(cp);
if (try_exp(cp, &operand))
return 1;
*result = pow(*result, operand);
}
return 0;
}
int try_primary(context *cp, double *result) {
switch (this_token(cp)) {
case OPERAND:
skip_token(cp);
*result = cp->value;
return 0;
case L_PARENTHESIS:
skip_token(cp);
cp->parenthesis_balance++;
if (try_add_sub(cp, result))
return 1;
cp->parenthesis_balance--;
if (this_token(cp) != R_PARENTHESIS) {
cp->error_code = PAREN_ERROR;
return 1;
}
skip_token(cp);
return 0;
}
cp->error_code = SYNTAX_ERROR;
return 1;
}
/* parse and evaluate an expression, return error code, update result */
int parse(char expression[], double *result) {
context cc;
cc.nextp = cc.p = expression;
cc.parenthesis_balance = 0;
cc.error_code = 0;
cc.value = 0;
if (try_add_sub(&cc, result))
return cc.error_code;
if (this_token(&cc) != TERMINAL)
return SYNTAX_ERROR;
return 0;
}
void solve(char expression[]) {
double result = 0;
switch (parse(expression, &result)) {
case 0:
printf(" %.17g\n", result);
break;
case SYNTAX_ERROR:
printf("ERROR: Syntax\n");
break;
case PAREN_ERROR:
printf("ERROR: Unbalanced parenthesis\n");
break;
}
}
//---- calculator.c ----
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//#include "parse.h"
int main(int argc, char **argv) {
for (int i = 1; i < argc; i++)
solve(argv[i]);
if (argc == 1) {
char user_in[1024];
char *p;
printf("Terminal Calculator\n");
printf("Type 'exit' to terminate\n\n");
for (;;) {
printf("=> ");
if (!fgets(user_in, sizeof user_in, stdin)) {
printf("\n");
break;
}
/* strip trailing newline */
user_in[strcspn(user_in, "\n")] = '\0';
/* skip initial white space */
p = user_in + strspn(user_in, " \t");
/* ignore empty and comment lines */
if (*p == '\0' || *p == '#')
continue;
/* trap exit command */
if (!strcmp(p, "exit"))
break;
solve(p);
}
}
return 0;
}
注入了我的班级：
clientProvider但是我收到一条错误消息：
@Inject
public DepictDao(@Named("depicts") Provider<ContentProviderClient> clientProvider) {
this.clientProvider = clientProvider;
}
当我尝试致电
Cannot return null from a non-@Nullable @Provides method