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For Hyp cos' extended array notation, see Strong array notation#Extended array notation.

Extended Array Notation (BEAN[1]) is a multidimensional version of Array notation, created by Jonathan Bowers.[2]

## Rules

These rules will be dropped to Main Rules and Array-Building Rules for conveniences.

### Notes

• Comma indicates $$(0)$$ separator.
• $$(x)$$ indicates that the rest of array goes to x-th dimension.
• $$(n_1)(n_2) \cdots (n_x)$$ indicates arbitrary number of separators such that $$n_1 \geq n_2 \geq n_3 \cdots \geq n_{x-1} \geq n_x$$.
• $$\&$$ means "array of" operator.
• $$\#$$ indicates any rest of array.

### Main Rules

Rule M1. Condition: only 2 entries.

$$\lbrace a,b \rbrace = a^b$$

Rule M2. Condition: 2nd entry is 1.

$$\lbrace a,1 \# \rbrace = a$$

Rule M3. Condition: $$n<m$$.

$$\lbrace \# (n) 1 (m) \# \rbrace = \lbrace \# (m) \# \rbrace$$

$$\lbrace \# (n) 1 \rbrace = \lbrace \# \rbrace$$

Rule M4. Condition: batch of separators before non-1 entry.

$$\lbrace a,b (n_1)(n_2) \cdots (n_x) c \# \rbrace = \lbrace b^{n_1} \& a (n_1) b^{n_2} \& a (n_2) \cdots b^{n_x} \& a (n_x) c-1 \# \rbrace$$

Rule M5. Condition: string of 1's between batch of separators and non-1 entry.

$$\lbrace a,b (n_1)(n_2) \cdots (n_x) 1,\cdots,1,c \# \rbrace = \lbrace b^{n_1} \& a (n_1) b^{n_2} \& a (n_2) \cdots b^m \& a (m) a,\cdots,\lbrace a,b-1 (n_1)(n_2) \cdots (n_x) 1,\cdots,1,c \# \rbrace,c-1 \#\rbrace$$

Rule M6. String of 1's in the main row.

$$\lbrace a,b,1,\cdots,1,c \#\rbrace = \lbrace a,a,a,\cdots,\lbrace a,b-1,1,\cdots,1,c \# \rbrace,c-1 \#\rbrace$$

Rule M7. Rules M1-M6 doesn't apply.

$$\lbrace a,b,c \#\rbrace = \lbrace a,\lbrace a,b-1,c \# \rbrace,c-1 \#\rbrace$$

### Array-Building Rules

Rule A1. $$n = 0$$.

$$b^0 \& a = a$$

Rule A2. Otherwise.

$$b^n \& a = \lbrace {(b-1)}^n \& a (n-1) b^{n-1} \& a \rbrace$$