Chapter 16. Reserved Keywords

Keywords can be used as ordinary symbols in many unambiguous situations. The precise rules are given in this chapter.

The free syntax of Rexx implies that some symbols are reserved for use by the language processor in certain contexts.

Within particular instructions, some symbols can be reserved to separate the parts of the instruction. These symbols are referred to as keywords. Examples of Rexx keywords are the WHILE keyword in a DO instruction and the THEN keyword, which acts as a clause terminator in this case, following an IF or WHEN clause.

Apart from these cases, only simple symbols that are the first token in a clause and that are not followed by an "=" or ":" are checked to see if they are instruction keywords. The symbols can be freely used elsewhere in clauses without being understood as keywords.

Be careful with host commands or subcommands with the same name as Rexx keywords. To avoid problems, enclose at least the command or subcommand in quotation marks. For example:

"DELETE" Fn"."Ext

You can then also use the SIGNAL ON NOVALUE condition to check the integrity of an executable.

Alternatively, you can precede such command strings with two adjacent quotation marks to concatenate the null string to the beginning. For example:

""Erase Fn"."Ext

A third option is to enclose the entire expression, or the first symbol, in parentheses. For example:

(Erase Fn"."Ext)