Pascal Report  167  8.2  Operators  the order of evaluation of the element descriptions in a set constructor  are implementation-dependent.  The evaluation of a factor consisting of a variable specifies an  access to the variable and denotes the value of the variable; it is an error  if the variable is undefined.  The evaluation of a factor consisting of a function designator  specifies an activation of the function that is denoted by the function  identifier (see Section 10.3). Any actual parameters are substituted for  their  corresponding  formal  parameters  (see  Section  11.3).  Upon  completion of the activation's algorithm, the factor denotes the value of  the result of the activation; it is an error if the result is undefined.  The rules of composition specify operator  precedences  according to  four classes of operators. The operator not has the highest precedence,  followed by the so-called mUltiplying operators, then the so-called  adding operators, and finally, with the lowest precedence, the relational  operators. Sequences of operators of the same precedence are executed  from left to right. The rules of precedence are reflected in the EBNF  rules for  Expression, Simple-Expression, Term,  and  Factor  (above).  Operators  are  also  classified  as  arithmetic,  Boolean,  set,  and  relational operators according to their operand and result types.  8.2.1. Arithmetic operators. An arithmetic operator takes integer or  real  operands  and  yields  an  integer or  real  results.  This  table  summarizes operators  that take one operand (the signs).  This table summarizes the operators that take two operands.  Operator  +  Operation  identity  sign inversion  Type of Operand  Integer or Real  Integer or Real  Type of Result  same as operand  same as operand  Operator  Operation  Type of Operands  Type of Result  +  addition  Integer or Real  Integer or Real  subtraction  Integer or Real  Integer or Real  *  multiplication  Integer or Real  Integer or Real  /  division  Integer or Real  Real  div  division  Integer  Integer  mod  modulo  Integer  Integer 