zclsyntax: enum for expression operations

Also includes the binary operator precedence table.

zcl/zclsyntax/expression_ops.go

@@ -0,0 +1,62 @@
+package zclsyntax
+
+type Operation rune
+
+const (
+	OpNil Operation = 0 // Zero value of Operation. Not a valid Operation.
+
+	OpLogicalOr          Operation = '∨'
+	OpLogicalAnd         Operation = '∧'
+	OpLogicalNot         Operation = '!'
+	OpEqual              Operation = '='
+	OpNotEqual           Operation = '≠'
+	OpGreaterThan        Operation = '>'
+	OpGreaterThanOrEqual Operation = '≥'
+	OpLessThan           Operation = '<'
+	OpLessThanOrEqual    Operation = '≤'
+	OpAdd                Operation = '+'
+	OpSubtract           Operation = '-'
+	OpMultiply           Operation = '*'
+	OpDivide             Operation = '/'
+	OpModulo             Operation = '%'
+	OpNegate             Operation = '∓'
+)
+
+var binaryOps []map[TokenType]Operation
+
+func init() {
+	// This operation table maps from the operator's token type
+	// to the AST operation type. All expressions produced from
+	// binary operators are BinaryOp nodes.
+	//
+	// Binary operator groups are listed in order of precedence, with
+	// the *lowest* precedence first. Operators within the same group
+	// have left-to-right associativity.
+	binaryOps = []map[TokenType]Operation{
+		{
+			TokenOr: OpLogicalOr,
+		},
+		{
+			TokenAnd: OpLogicalAnd,
+		},
+		{
+			TokenEqual:    OpEqual,
+			TokenNotEqual: OpNotEqual,
+		},
+		{
+			TokenGreaterThan:   OpGreaterThan,
+			TokenGreaterThanEq: OpGreaterThanOrEqual,
+			TokenLessThan:      OpLessThan,
+			TokenLessThanEq:    OpLessThanOrEqual,
+		},
+		{
+			TokenPlus:  OpAdd,
+			TokenMinus: OpSubtract,
+		},
+		{
+			TokenStar:    OpMultiply,
+			TokenSlash:   OpDivide,
+			TokenPercent: OpModulo,
+		},
+	}
+}