Contract: Iterate each char inside string and numerical value check

Question

For example I have following string, which will be given as input from a user:

string str = "0-00:03"

Inside my contract I would like to check that:

• str[1] should be -
• str[4] should be :
• and the remaining characters have to be numeric value.

This operation is easy to do C where with pointer I can iterate each character and check its char value. But I was not able to operate this inside my contract under Solidity language.

Answer 1

Just cast the string to bytes

function testStr(string str) constant returns (bool) {
    bytes memory b = bytes(str);
    if (b.length != 7)
        return false;
    for (uint i; i < 7; i++) {
        if (i==1) {
            if(b[i] != 45) return false;
        }
        else if (i == ) {
            if(b[i] != 58) return false;
        }
        else if(b[i] < 48 || b[i] > 57)
            return false;
    }
    return true;
}