How to create an array of const structs

arrays, c, struct

Solution

Variables with static storage duration have to have compile-time constant initializers in C. And another variable does not count as a compile-time constant (even if that variable is const).

You could write:

#define MAJOR_ARP {3,"Major Arpeggio",{0.0,JUST_MAJ_3,JUST_PERF_5}}
#define MINOR_ARP {3,"Minor Arpeggio",{0.0,JUST_MIN_3,JUST_PERF_5}}

const ARPINFO majorArp = MAJOR_ARP;
const ARPINFO minorArp = MINOR_ARP;

const ARPINFO arpInfoArray[2] = { MAJOR_ARP, MINOR_ARP };

Note that this has two copies of your data. If you're OK with having one copy of the data and the other static variables referencing it, you could instead do:

const ARPINFO *const arpInfos[2] = { &majorArp, &minorArp };

Problem

I want to be able to create const structs with specific info easily, so have decided to declare and initialise them "one-line-at-a-time", so I can simply add new const structs as I need them. This works fine, but how can I create some kind of array to access each of these const structs? I tried the following, but it doesn't work. ``` typedef struct { int numOfNotes; char *arpName; double freqRatios[12]; } ARPINFO; const ARPINFO majorArp = {3,"Major Arpeggio",{0.0,JUST_MAJ_3,JUST_PERF_5}}; const ARPINFO minorArp = {3,"Minor Arpeggio",{0.0,JUST_MIN_3,JUST_PERF_5}}; const ARPINFO arpInfoArray[2] = {majorArp,minorArp}; // ERROR HERE ``` If I can use this way of organising my structs, I'll only have to change the size of the array and add the new const struct to the array, each time I create a new const struct. Or am I way off track here? Would enums or MACROS help me out? EDIT: The freqRatios are defined with macros and I understand that the initial 0.0 is likely to be redundant...

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