User blog comment:Tetramur/The new formalization of BEAF/@comment-35470197-20200222073359/@comment-35470197-20200222085117

There are so many common mistakes listed here.

> Valid expression has form A&n, where A is structure.

Quantify all new symbol (here, n) and Define all new terminology (here, structure). See "Lack of the Declaration" in the list.

> 1. 0&n and 1&n are both valid expressions.

Quantify all new symbol (here, n). See "Lack of the Declaration" in the list.

> 2. The sum, product and exponent of valid expressions are valid (that is, X^7&n + X^3&n = (X^7+X^3)&n).

Ill-defined by the mixing of operation and formal symbol. See "Undefined Comparison" and "Undefined Operation" in the list.

> 3. If Knuth's arrows and linear arrays are applied to valid expressions, they are still valid.

Ill-defined by the mixing of operation and formal symbol. See "Undefined Operation" in the list.