c_0_52
ord_less_eq_real @ one_one_real @ ( round_down @ p @ x )
Proof
lemma round_down_ge1: assumes x: "x ≥ 1" assumes prec: "p ≥ - log 2 x" shows "1 ≤ round_down p x"
also have "… ≤ ⌊2 powr 0::real⌋" by simp
also have "… ≤ ⌊x * 2 powr (real_of_int p)⌋"
unfolding of_int_le_iff
using x x_le by (intro floor_mono) (simp add: powr_minus_divide field_simps)
finally show ?thesis
using prec xord_less_eq_real @ one_one_real @ ( round_down @ p @ x )