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Major elements to construct expressions are the following:
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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
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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[0] M[1][2]
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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.
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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.
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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.)
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function call
A function call is also an expression.
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`++', `--'
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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