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The Compleat User RPL Encyclopedia


x y    x=y
Keyboard Access:
  HP-28: the = key
   HP48: LS-0
HP49/50: RS-[+/–]
Equals analytic function: Returns an equation formed from the two arguments.

The equals sign equates two expressions such that the difference between them is zero.

In Symbolic Results mode, the result is an algebraic equation. In Numerical Results mode, the result is the difference of the two arguments because  acts equivalent to (subtraction). This allows expressions and equations to be used interchangeably as arguments for symbolic and numerical rootfinders.

Caution! is NOT a “test” function! It is mathematically the same as subtraction! This can cause no end of consternation when accidentally used as a test, when should have been used, as can be seen in the first two highly counter-intuitive examples below:

(Surprise! It’s because  means  which is 0 which is a FALSE!)

(Surprise! It’s because  means  which is 1 which is a TRUE!)

(because  means '1 is equal to 1' which is TRUE.)

(because  means '2 is equal to 1' which is FALSE.)
Therefore, remember to use  when you want to TEST for equality! Only use  in mathematical equations! YOU HAVE BEEN WARNED.

See also:

BYTES: 2.5