# Re: A notation convenience for certain non-linear expressions

Mok-Kong Shen wrote:

If f11(x) etc. are functions of x, one can namely e.g. use

| f11 f12 | | x1 |
| | * | |
| f21 f22 | | x2 |

to express the vector

| f11(x1) + f12(x2) |
| |
| f21(x1) + f22(x2) |

[Addendum] One could evidently, if desired, also adopt the convention
that in the vector above + be substituted by xor, while leaving the
functions unchanged. On the symbolic level, one could write/discuss
M1*M2, M^(-1), C = M * P, etc., as is familiar in linear algebra.

M. K. Shen

.

## Relevant Pages

• Re: uses of xor
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• Re: A notation convenience for certain non-linear expressions
... One could evidently, if desired, also adopt the convention ... that in the vector above + be substituted by xor, while leaving the ... Addition by XOR is just addition over Z_2 if your matrix elements are ...
(sci.crypt)