Hand Sign Pic Game

[juji]

Post a picture if you guessed right.

"Making a sideways fist, fingers facing the receiver, moving it left and right and simultaneously poking the inside of the opposite cheek with the tongue so it bulges out."

[jon]

5. $sublis [x; y]$. Here $x$ is assumed to have the form of a list of pairs $((u_1, v_1), \cdots, (u_n, v_n))$, where the $u$'s are atomic, and $y$ may be any S-expression. The value of $sublis [x; y]$ is the result of substituting each $v$ for the corresponding $u$ in $y$. In order to define sublis, we first define an auxiliary function. We have

\begin{displaymath}sub2 [x; z] = [null [x] \rightarrow z; eq [caar [x]; z]
\rightarrow cadar [x]; T \rightarrow sub2 [cdr [x]; z]]\end{displaymath}

and
\begin{displaymath}sublis [x; y] = [atom [y] \rightarrow sub2 [x; y];
T \rightarrow cons [sublis [x; car [y]]; sublis [x; cdr [y]]]\end{displaymath}

We have
sublis [((X, (A, B)), (Y, (B, C))); (A, X $\cdot$ Y)] = (A, (A, B), B, C)

[Cody]