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- Unary operators and assignments are evaluated from right to left.
- Binary operators are evaluated according to their priority and from left to right.
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Binary operators in ascending order
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|| ^^
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Lowest priority
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&&
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= != <> > >= < <=
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+ - | ^
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* / // \ \\ &
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**
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Highest priority
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Logical expressions are evaluated completely, no lazy (or short-circuit) evaluation is used !
Expression examples:
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a := 10
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Expression is a simple assignment, a is assigned the value 10.
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a := b := c := 10
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a, b and c are assigned the value 10. The variable c is assigned first, b second and the variable a last.
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a+1 < 10
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The priority of the + operator exceeds the priority of the < operator thus the sub-expression a+1 is evaluated first.
If the variable a has a value equal to or greather than 9 before the expression is evaluated the result of the expression will be FALSE.
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1+2*3
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The priority of the * operator exceeds the priority of the + operator thus the result will be 7.
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(1+2)*3
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The sub-expression between the parentheses is evaluated first so that the result will be 9.
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FALSE && (a:=a+1)
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The value of the variable a is incremented although the first sub-expression is FALSE. No lazy evaluation is applied as it is used in some other languages. (e.g. Pascal)
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a=0 && b>10 || a!=0 && b<-10
is similar to
((a = 0) && (b > 10)) || ((a != 0) && (b < -10))
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a := -b := 1
is invalid and should be
a := -(b := 1)
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The first expression is not allowed! The assignment operator := cannot assign a value to an expression.
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!(a && b) is similar to !a || !b
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