Why the switch statement cannot be applied on strings?

Question

Compiling the following code and got the error of type illegal.

int main()
{
    // Compilation error - switch expression of type illegal
    sw         


        

Answer 1

That's because C++ turns switches into jump tables. It performs a trivial operation on the input data and jumps to the proper address without comparing. Since a string is not a number, but an array of numbers, C++ cannot create a jump table from it.

movf    INDEX,W     ; move the index value into the W (working) register from memory
addwf   PCL,F       ; add it to the program counter. each PIC instruction is one byte
                    ; so there is no need to perform any multiplication. 
                    ; Most architectures will transform the index in some way before 
                    ; adding it to the program counter

table                   ; the branch table begins here with this label
    goto    index_zero  ; each of these goto instructions is an unconditional branch
    goto    index_one   ; of code
    goto    index_two
    goto    index_three

index_zero
    ; code is added here to perform whatever action is required when INDEX = zero
    return

index_one
...

(code from wikipedia https://en.wikipedia.org/wiki/Branch_table)