∆ḟ
Characters: ∆, ḟ
∆
ḟ
Get the previous power of b before a.
num-num
b ** ceil(log(a, b) - 1)
10 10 ∆ḟ
1
9 10 ∆ḟ
11 10 ∆ḟ
10
4 2 ∆ḟ
2
17 3 ∆ḟ
9
100 10 ∆ḟ