This manual contains a number of examples of m4 input and output,
and a simple notation is used to distinguish input, output and error
messages from m4. Examples are set out from the normal text, and
shown in a fixed width font, like this
This is an example of an example!
To distinguish input from output, all output from m4 is prefixed
by the string `=>', and all error messages by the string
`error-->'. Thus
Example of input line =>Output line from m4 error-->and an error message
As each of the predefined macros in m4 is described, a prototype
call of the macro will be shown, giving descriptive names to the
arguments, e.g.,
regexp(string, regexp, opt replacement)
All macro arguments in m4 are strings, but some are given special
interpretation, e.g., as numbers, filenames, regular expressions, etc.
The `opt' before the third argument shows that this argument is optional--if it is left out, it is taken to be the empty string. An ellipsis (`...') last in the argument list indicates that any number of arguments may follow.
This document consistently writes and uses builtin, without an
hyphen, as if it were an English word. This is how the builtin
primitive is spelled within m4.
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