Picture language

In formal language theory, a picture language is a set of pictures, where a picture is a 2D array of characters over some alphabet.

For example, the language ${\displaystyle L=\left\{a^{n,n+1}\mid n>0\right\}}$ defines the language of squares composed of the character ${\displaystyle a}$. This language ${\displaystyle L}$ contains pictures such as:

${\displaystyle {\begin{pmatrix}a\\a\end{pmatrix}},{\begin{pmatrix}a&a\\a&a\\a&a\end{pmatrix}},{\begin{pmatrix}a&a&a\\a&a&a\\a&a&a\\a&a&a\end{pmatrix}}\in L}$

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