Can use circom 2.1 feature for array constraints

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Circom 2.1 allows using <== operator for signal arrays (documentation). You can avoid writing loops just to assign inputs to a component.

For example:

-for (var i = 0; i < k; i++) {
-    g_pow_s.privkey[i] <== s[i];
-}
+g_pow_s.privkey <== s