SPECIAL
SYMBOLS IN ISETL

****** Exponentiation. Example: **2**3
= 8
**

**:=**
Assignment. Used to define values for variables. These variables can
represent any mathematical object: a number, a Boolean, a set, a tuple, a
string, a function. Example: **f := func(x);** etc.

**/=** Inequality. This
means "not equal to".

**#** This can be
either cardinality of a set or length of a tuple. Example: **#{1,3,1}= 2; #[1,3,1] = 3;
**

**..**
Iteration. Used to create arithmetic sequences of numbers, especially in
sets or tuples. Examples: **{1..9}; [9,8..1];
**

**:**
"Such that". Used in set formers and tuple formers. Also used
in quantified expressions.

Example: **S := { x : x in
{10..99} | x mod 6 = 0 };
**

**|** Same as
the colon. ** exists x in S | x div 5 = 0;**

**$** Comment symbol.
The rest of this line will not be processed.

**%
**Used
to change a binary operation into something that works for an entire set or
tuple. For instance, addition is a binary operation because you can only add two
numbers at a time, like this: **1 + 2 = 3. ** To
add more than two numbers, put the % sign in front of the operator.

Examples: **%+{1..9} = 45; %max{1..9} = 9;
%*{1..9} = 362880;
**(The last
example shows a nice way to do factorials.)