theorem droplen (l n: nat): $ len (drop l n) = len l - n $;
| Step | Hyp | Ref | Expression |
|---|
| 1 |
|
lenlfn |
len (lfn (\ a1, nth (a1 + n) l - 1) (len l - n)) = len l - n |
| 2 |
1 |
conv drop |
len (drop l n) = len l - n |
Axiom use
axs_prop_calc
(ax_1,
ax_2,
ax_3,
ax_mp,
itru),
axs_pred_calc
(ax_gen,
ax_4,
ax_5,
ax_6,
ax_7,
ax_10,
ax_11,
ax_12),
axs_set
(elab,
ax_8),
axs_the
(theid,
the0),
axs_peano
(peano1,
peano2,
peano5,
addeq,
muleq,
add0,
addS,
mul0,
mulS)