Even and Odd Operators
Date: 2020-10-07 18:10:00

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### 7.17 Even and Odd Operators

An operator can be declared to be even or odd in its ﬁrst argument by the declarations EVEN and ODD respectively. Expressions involving an operator declared in this manner are transformed if the ﬁrst argument contains a minus sign. Any other arguments are not aﬀected. In addition, if say F is declared odd, then f(0) is replaced by zero unless F is also declared non zero by the declaration NONZERO. For example, the declarations

even f1; odd f2;

mean that

f1(-a) -> F1(A)
f2(-a) -> -F2(A)
f1(-a,-b) -> F1(A,-B)
f2(0) -> 0.

To inhibit the last transformation, say nonzero f2;.

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