Explain how to write conditions in circom

Conditons in circom

// THIS IS BAD
template BadExample() {
    signal input a;
    signal input b;
    signal output c;
    if (a==1) {
        c <== b*b;
    } else {
        c <== b+5;
    }
}
component main = BadExample()

/// THIS IS GOOD

include "node_modules/circomlib/circuits/mux1.circom";
include "node_modules/circomlib/circuits/comparators.circom";

template GoodExample() {
    signal input a;
    signal input b;
    signal output c;

    component eq1 = IsEqual()
    eq1.in[0] <== a;
    eq1.in[1] <== 1;

    component mux1 = Mux1();
    mux1.s <== eq1.out;
    mux1.c[0] <== b*b;
    mux1.c[1] <== b+5;

    c mux1.out;
}

component main = GoodExample()