PS TEXT FORMAT Reference Manual

5 Expressions
11387 Tandem Computers Incorporated 5-1
Introduction An expression is an item of data in various forms that TFORM evaluates to
a single value. TFORM expressions can be any of the following:
A single digit, a single-letter variable name, or a 1-character string (a
string is zero or more characters enclosed in quotation marks)
A combination of digits, with or without a decimal point, to make a
large number
A long variable name, perhaps containing multiple words joined by
underscore characters or perhaps enclosed in an indirection escape
sequence
A collection of letters, numbers, and punctuation marks (including
spaces), enclosed in quotes, that constitutes a longer string
A function name and a list of arguments for the function, enclosed in
parentheses
A combination of all of these with operators, which define activities to
be performed on the numbers, variables, or strings
Whenever TFORM sees an expression (in a place where expressions are
allowed), it evaluates that expression, performing whatever computations
and comparisons are necessary (specified in the expression by operators) to
reduce it to a single value. TFORM then uses the value as appropriate in
the execution of a command.