5. Expressions

An expression is composed of integers, identifiers, and operators.

5.1. Operators

Operators are listed in descending precedence order. Operators without a horizontal line dividing them have equal precedence. For example, addition and subtraction have an equal level of precedence.

Class	Operation	Symbol	Usage	Associativity
Arithmetic	multiplication division	* /	expr * expr expr / expr	left left
	addition subtraction	+ -	expr + expr expr - expr	left left
Comparison	less than greater than	< >	expr < expr expr > expr	left left
	is equal is not equal	== !=	expr == expr expr != expr	left left

Clarification: There is no remainder operator in SCalc. (no-rem)

Clarification: There is no exponentiation operator in SCalc. (no-pow)

Clarification: Division is integer division. (int-div)

5.2. Valid Expressions

Valid formats for expressions are

(<expr>)
<expr> <op> <expr>
<int>
<id>

• expr is an expression.

• int is an integer.

• id is the identifier of a variable.

Assertion: All expressions will result in a value that fits in a 32 bit signed integer. (expression-size)

Assertion: No expression will contain a division by 0. (zero-divide)

Examples of valid expressions are

i * 2 * 10 + 4
2 - 4 * 5

5.3. Precedence

Precedence determines what order operations are evaluated in. Precedence works as defined in the following table:

Precedence	Operations
HIGHER	* /
	+ -
	< >
LOWER	== !=