PS TEXT FORMAT Reference Manual

Escape Sequences
11387 Tandem Computers Incorporated 4-11
Double Indirection Another way of using the indirection escape sequence is with “double
indirection” (sort of “the-value-of-the-value-of"). You do this by doubling
the trigger character at the start and end of the escape sequence. Such an
escape sequence would look like this:
\\VALUE ( exp \\)
or simply:
\\( exp \\)
You use double indirection in commands that contain a title, primarily the
CONTENTS, HEADER, and FOOTER commands. TFORM performs a pre-
execution scan on such commands when it first encounters them,
evaluating any expressions they may contain. When TFORM finds
doubled triggers, it converts them to single triggers without evaluating the
contained expression. (Recall that TFORM interprets a doubled trigger
character as a literal trigger character, not as the beginning of a command
or escape sequence.) The expression remains enclosed as an indirection
escape sequence, ready to be evaluated whenever the command is
executed.
When TFORM does its pre-execution scan, it converts a standard
indirection escape sequence such as \( exp \) to the current value of exp; the
actual value appears at that point in the output. However, TFORM
converts \\( exp \\) with double triggers to \( exp \) and delays evaluation
of the expression.