EXPRESSI.HELPREXX

Expression

+-----------------------------------------------------------------------------+
| expression is: term [operator term [operator term [...]]]                   |
|                                                                             |
| term is: prefix_operator term | literal_string | symbol | function_call |   |
|          '(' expression ')                                                  |
|                                                                             |
| operator is: '+' | '-' | '*' | '/' | '//' | '**' | '||' | '=' | '^=' | '%' ||
|              '\=' | '>' | '<' | '<>' | '><' | '>=' | '^=' | '\<' | '<=' |   |
|              '^>' | '\>' | '==' | '^==' | '\==' | '>>' | '<<' | '>>=' |     |
|              '^<<' | '\<<' | '<<=' | '^>>' | '\>>' | '&' | '|' | '&&' |     |
|                                                                             |
| prefix_operator is '-' | '+' | '^' | '\'                                    |
|                                                                             |
| literal_string is: "'" characters "'" | '"' characters '"' *                |
|                                                                             |
| symbol is: variable_name | number                                           |
|                                                                             |
| function_call is: function_name '(' [expression], [expression], ...)        |
|                                                                             |
| function_name is: string | symbol                                           |
|                                                                             |
| number is: whole_number | decimal_number | exponential_number               |
|                                                                             |
| * If the characters include the same quote as they are enclosed in, it must |
|   be doubled.  For example, '''' is a 1-character string consisting of one  |
|   single quote.  The same value can be written as "'" without doubling.     |
+-----------------------------------------------------------------------------+

An expression is a series of terms and operators, processed in order by
operator precedence, as modified by parantheses:

    1) Parentheses: '(', ')'
    2) Prefix operators: '+', '-', '^', '\'
    3) Exponentiation: '**'
    4) Multiplication and division: '*', '/', '%', '//'
    5) Addition and subtraction: '+', '-'
    6) Concatenation: '||', blank, abuttal
    7) Comparison: '=', '^=', '\=', '>', '<', '<>', '><', '>=', '^=', '\<',
                   '<=', '^>', '\>', '==', '^==', '\==', '>>', '<<', '>>=',
                   '^<<', '\<<', '<<=', '^>>', '\>>'
    8) Logical And: '&'
    9) Logical Or, Xor: '|', '&&'

A whole_number is composed of decimal digits (i.e., '0'-'9').  A decimal_number
is composed of a whole_number (the "integer part"), a period ('.'), and
another whole_number (the "decimal part").  An exponential_number is composed
of a decimal_number and an exponent ('E' or 'e' followed by a whole_number),
with an implied base of 10.

Examples: