Converting string to decimal, not working for some cases? - c

Question

i am trying to take a string and seeing if it could be converted into decimal/float/octal/hex
I have stored these strings into an array, and im iterating through them and checking which element is what.
for(int k=0;k<i;k++){
char* string = tokenArray[k];
fprintf(newFile, "Tokens are: %s\n", string);
if(checkDecimal(string) == 1){
result[k] = "Decimal"; printf("Token: %s is %s\n", string, result[k]);
}
else if(checkFloat(string) == 1){
result[k] = "Float"; printf("Token: %s is %s\n", string, result[k]);
}
else if(checkHex(string) == 1){
result[k] = "Hex"; printf("Token: %s is %s\n", string, result[k]);
}
else if(checkOctal(string) == 1){
result[k] = "Octal"; printf("Token: %s is %s\n", string, result[k]);
}
else {
printf("Token: %s Did not work\n", string);
}
I wrote contents of my array into a separate file which is, :
fprintf(newFile, "Tokens are: %s\n", string);
Tokens are: 012
Tokens are: 23948
Tokens are: 1.21e+19
Tokens are: [
Tokens are: ,
Tokens are: 0
Tokens are: 0x56
Tokens are: 888
Tokens are: 0X11
Tokens are: 12
Tokens are: 333
Tokens are: 234
Tokens are: 012
Tokens are: 12
Tokens are: 01200
As you can see i am getting the tokens correctly, but my output is coming up weird.
This is my code for checking elements:
int checkFloat(char *s){
char *str = NULL;
long i = strtol(s, &str, 0);
if (!*str)
return 0;
if (*str == 'e' || *str == 'E' || *str == '.')
return 1;
return 0;
}
int checkHex(char *s){
char *str = s;
if((*str) == '0'){
if((*(str++) == 'x')){
printf("%s\n", "olala");
}
}
if(*(str) == 0 && (*(str++) == 'x' || *(str++) == 'X'))
{
printf("%s\n", "ok");
while(*(str) != '\0')
{
if (!isxdigit(*str))
{
return 0;
}
++str;
}
return 1;
}
return 0;
}
int checkOctal(char *s){
char *str = s;
if (*str != '0')
{
return 0;
}
while (isdigit(*str) && *str != '8' && *str != '9')
{
if(*(++str) == '\0')
{
return 1;
}
str++;
}
return 0;
}
int checkDecimal(char *s){
char *str = s;
if(*str == '0')
return 0;
for(int i=0;i<strlen(str);i++){
if(str[i] < 49 || str[i] > 57)
return 0;
}
return 1;
}
I think these functions are fine,
this is the output:
Token: 012 is Octal
Token: 23948 is Decimal
Token: 1.21e+19
is Float
Token: [ Did not work
Token: , Did not work
Token: 0 is Octal
Token: 0x56 Did not work
Token: 888 is Decimal
Token: 0X11
Did not work
Token: 12 is Decimal
Token: 333 is Decimal
Token: 234
Did not work
Token: 012
Did not work
Token: 12 is Decimal
Token: 01200 is Octal
As you can see, first token was 012 which came out as octal (fine). Another token with same 012 came out as error. Same with "234".
I dont know why my hex fucntion dosent work either.
Plz help

Answer 1

Your code's most outstanding issue is your use of '++' (increment). You tend to overuse it, skipping over characters you intend to test. E.g. consider a clause like:
(*(str) == 0 && (*(str++) == 'x' || *(str++) == 'X'))
Which can leave the pointer in two different locations and fails to test for 'X' as it's looking at the wrong character. This really should be:
(*str++ == '0' && (*str == 'x' || *str == 'X'))
Your code is riddled with this type of error. (As well as confusing 0 with '0' as noted in the comments.) Fixing your increments and generally reworking your code:
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
typedef enum { FALSE = 0, TRUE } boolean;
int checkFloat(char *s) {
char *extra = NULL;
(void) strtol(s, &extra, 0);
return ((*extra != '\0') && (*extra == 'e' || *extra == 'E' || *extra == '.'));
}
int checkHex(char *s) {
char *str = s;
if (*str++ == '0' && (*str == 'x' || *str == 'X')) {
while (*(++str) != '\0') {
if (!isxdigit(*str)) {
return FALSE;
}
}
return TRUE;
}
return FALSE;
}
int checkOctal(char *s) {
char *str = s;
if (*str++ != '0') {
return FALSE;
}
while (isdigit(*str) && *str != '8' && *str != '9') {
if (*(++str) == '\0') {
return TRUE;
}
}
return FALSE;
}
int checkDecimal(char *s) {
char *str = s;
if (*str == '0') {
return FALSE; // looks like octal
}
for (size_t i = 0; i < strlen(str); i++) {
if (str[i] < '1' || str[i] > '9') {
return FALSE;
}
}
return TRUE;
}
char *tokenArray[] = {
"012",
"12948",
"1.21e+19",
"[",
",",
"0",
"0x56",
"888",
"0X11",
"12",
"333",
"234",
"012",
"12",
"01200"
};
#define TOKEN_COUNT (sizeof(tokenArray) / sizeof(char *))
int main() {
char *result[TOKEN_COUNT];
for (size_t k = 0; k < TOKEN_COUNT; k++) {
char *string = tokenArray[k];
if (checkDecimal(string)) {
result[k] = "Decimal";
printf("Token: %s is %s\n", string, result[k]);
} else if(checkFloat(string)) {
result[k] = "Float";
printf("Token: %s is %s\n", string, result[k]);
} else if (checkHex(string)) {
result[k] = "Hex";
printf("Token: %s is %s\n", string, result[k]);
} else if (checkOctal(string)) {
result[k] = "Octal";
printf("Token: %s is %s\n", string, result[k]);
} else {
printf("Token: %s Did not work\n", string);
}
}
return 0;
}
Produces:
Token: 012 is Octal
Token: 12948 is Decimal
Token: 1.21e+19 is Float
Token: [ Did not work
Token: , Did not work
Token: 0 Did not work
Token: 0x56 is Hex
Token: 888 is Decimal
Token: 0X11 is Hex
Token: 12 is Decimal
Token: 333 is Decimal
Token: 234 is Decimal
Token: 012 is Octal
Token: 12 is Decimal
Token: 01200 is Octal
In general, style-wise, you should pick an indentation/bracketing style you like and stick with it consistenly -- your code is all over the place.