to answer your original question, it is not possible to get the enum value from a string in C. (however, the reverse is possible using the stringizing preprocessor operator, but it will not help in your case.)
back to your problem, i can see no problem getting the enum value from a character by subtracting 'A'. here is how i would do it:
// this is the original enum defining the
typedef enum
{
A=3,
B=5,
C=12,
D=22,
E=48,
...
} index;
// this array is a lookup table: it shall be indexed by letters starting with 'A'
// and contains the enum value associated with each letter
index lut['Z'-'A'+1] = {A,B,C,D,E, ...};
// if this is the input string and the ouput array
char string[21]= "AAABBBCCDDDDDEABDECD";
index lind[21]; // adjust the size of this array, or allocate it dynamically to suit your needs
// now conversion takes the form of
unsigned int i = 0;
while ( string[i] != '\0' )
{
if ( (string[i] < 'A') && (string[i] > 'Z') ) // you shall always verify user input !
exit( -1 ); // take appropriate actions in case of input error
lind[i] = lut[ string[i]-'A' ];
i++;
}
there can be a great number of variations on this code: using string replace functions of the standard library, using characters pointers to factorout the index of the string, etc...
anyway, i fear that you got your problem wrong. what you are writing looks a lot like a parser: a user provides an input that you read and convert to something useful for your program. if the input string is given by a user, this solution works (while there may be a more extensible solution). remember, that user input shall always be validated, and error checking code might take a lot more than the single line in the example above because a parser has to be fool-proof and fail gracefully in case of error. however, if the input string is coded in your own program, then this approach is definitely bad: inefficient, error prone, the solution does not represent the problem space. if you tell us more about your program, we would be able to tell you more about a solution.
