Checking a string for a valid number

[nano2]

hi

have the following case want to check a string to see if is a valid number
can anyone spot whats wrong with the following if statement


char *ch
for (i = 0; i < strlen(ch); i++){
if ((ch[i] >= '0') && (ch[i] <= '9') && ( i < strlen(ch) ) || (ch[i] == '.') )
// It's a Number

[Ganon11]

You should have a bool variable indicating whether it is a number or not. During the execution of the for... loop, if the current character is NOT numeric, set the variable to false - it is no longer a number. At the end of the loop, the variable will be true if every character was numeris and false otherwise.

[nano2]

You should have a bool variable indicating whether it is a number or not. During the execution of the for... loop, if the current character is NOT numeric, set the variable to false - it is no longer a number. At the end of the loop, the variable will be true if every character was numeris and false otherwise.

What i have now but it returns True ( thats a number )for the following 214214.000
BoolFlag = 0;
for (i = 0; i < strlen(ch); i++){
if ((ch[i] >= '0') && (ch[i] <= '9') && ( i < strlen(ch) ) && (BoolFlag != 1) || (ch[i] == '.') ){
BoolFlag = 1; /* Number */
}
else{
BoolFlag = 0; /* string */
}

}
return BoolFlag;

[horace1]

your expression is a bit complex - if any of the tests fail, i.e. the character is not 0 to 9 or . you return immediatly with fail
e.g.

for (i = 0; i < strlen(ch); i++)
  if (!((ch[i] >= '0') && (ch[i] <= '9') || (ch[i] == '.')) )
   return 0;    // fail
return 1; /* Number */