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3.2 Basic Expressions

In the following descriptions of legal expressions, "expr" refers to a complete expression and "var" refers to a simple or an array variable. A simple variable is just a

name

and an array variable is specified as

name[expr]

Unless specifically mentioned the scale of the result is the maximum scale of the expressions involved.

- expr

The result is the negation of the expression.

++ var

The variable is incremented by one and the new value is the result of the expression.

-- var

The variable is decremented by one and the new value is the result of the expression.

var ++

The result of the expression is the value of the variable and then the variable is incremented by one.

var --

The result of the expression is the value of the variable and then the variable is decremented by one.

expr + expr

The result of the expression is the sum of the two expressions.

expr - expr

The result of the expression is the difference of the two expressions.

expr * expr

The result of the expression is the product of the two expressions.

expr / expr

The result of the expression is the quotient of the two expressions. The scale of the result is the value of the variable scale

expr % expr

The result of the expression is the "remainder" and it is computed in the following way. To compute a%b, first a/b is computed to scale digits. That result is used to compute a-(a/b)*b to the scale of the maximum of scale+scale(b) and scale(a). If scale is set to zero and both expressions are integers this expression is the integer remainder function.

expr ^ expr

The result of the expression is the value of the first raised to the second. The second expression must be an integer. (If the second expression is not an integer, a warning is generated and the expression is truncated to get an integer value.) The scale of the result is scale if the exponent is negative. If the exponent is positive the scale of the result is the minimum of the scale of the first expression times the value of the exponent and the maximum of scale and the scale of the first expression. (e.g. scale(a^b) = min(scale(a)*b, max(scale, scale(a))).) It should be noted that expr^0 will always return the value of 1.

( expr )

This alters the standard precedence to force the evaluation of the expression.

var = expr

The variable is assigned the value of the expression.

var <op>= expr

This is equivalent to "var = var <op> expr" with the exception that the "var" part is evaluated only once. This can make a difference if "var" is an array.


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