CODEWITHSUNDEEP
cscopec-preprocessor
MrWolvwxyz
MrWolvwxyz

Reputation: 93

#Define Variables Scope

I am wondering if there is a way to define a global variable that has the name of a specific instance from my main function? I have to access an array by bit values so to do that I need to type:

state.reg[ 4 * mc_binary[ 18 ] + 2 * mc_binary[ 17 ] + 1 * mc_binary[ 16 ] ]

Can I have:

#define state.reg[ 4 * mc_binary[ 18 ] + 2 * mc_binary[ 17 ] + 1 * mc_binary[ 16 ] ] registerA

where state is my instance of a stateType struct that is used in my main function?

Upvotes: 1

Views: 111

Answers (1)

steveha
steveha

Reputation: 76765

This is what I would recommend:

#define BIT_INDEX3(bit2, bit1, bit0) \
    (4 * (bit2) + 2 * (bit1) + (bit0))

// use in code:
    state.reg[ BIT_INDEX3(mc_binary[18], mc_binary[17], mc_binary[16]) ]

You don't want to get too tricky, but if you will often be pulling from the same array (as you did here) you could make another define for that:

#define BIT_INDEX_ARRAY3(a, i2, i1, i0) \
    BIT_INDEX3((a)[i2], (a)[i1], (a)[i0])


// use in code:
state.reg[ BIT_INDEX_ARRAY3(mc_binary, 18, 17, 16) ]

Upvotes: 2

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