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### various expressions

Major elements to construct expressions are the following:

• addition, subtraction, multiplication, division, exponentiation
The exponentiation is denoted by `^'. (This differs from C language.) Division denoted by `/' is used to operate in a field, for example, `2/3` results in a rational number `2/3`. For integer division and polynomial division, both including remainder operation, built-in functions are provided.
```x+1  A^2*B*afo X/3
```
• programming variables with indices
An element of a vector, a matrix or a list can be referred to by indexing. Note that the indices begin with number 0. When the referred element is again a vector, a matrix or a list, repeated indexing is also effective.
```V M
```
• comparison operation
There are comparison operations `==' for equivalence, `!=' for non-equivalence, `>', `<',`>=', and `<=' for larger or smaller. The results of these operations are either value 1 for the truth, or 0 for the false.
• logical expression
There are two binary logical operations `&&' for logical `conjunction'(and), `||' for logical `disjunction'(or), and one unary logical operation `!' for logical `negation'(not). The results of these operations are either value 1 for the truth, and 0 for the false.
• assignment
Value assignment of a program variable is usually done by `='. There are special assignments combined with arithmetic operations. (`+=', `-=', `*=', `/=', `^=')
```A = 2  A *= 3 (the same as A = A*3; The other combination are alike.)
```
• function call
A function call is also an expression.
• `++', `--'
These operators are attached to or before a program variable, and denote special operations and values.
```A++  the expression value is the previous value of A, and A = A+1
A--  the expression value is the previous value of A, and A = A-1
++A  A = A+1, and the expression value is the value after increment of A
--A  A = A-1, and the expression value is the value after decrement of A
```

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