Editing Module:Road data/strings/doc (section)

===Basic string syntax===
The most basic value that can be used for most type table fields is a specially formatted string, which will be referred to in this documentation as a ''format string''. This is the string that will ultimately be parsed and returned by the parser. A format string is an ordinary string object. The power of these strings comes in the form of two special instructions that are recognized by the parser.

The first is anything in <code>%argument%</code> form. The parser will replace such a statement with the value of the <code>argument</code> entry in the arguments table described earlier. This is what allows the route number to be spliced into a shield or link name.

The second special string is in the form of <code>[arg|equals|then|else]</code>. This functions as a rudimentary if-then-else statement. The parser tests the value of <code>arg</code> to see if it is equal to the value specified in <code>equals</code>. <code>equals</code> may be empty, in which case the parser tests the existence of the <code>arg</code> argument. If the result of the test is true, the statement is replaced with the value of the <code>then</code> block. Otherwise, it is replaced with the value of the <code>else</code> block.

The two statements may be combined. The parser will parse the if-then-else statement first, and then perform the argument inclusion. This combination is commonly used with bannered routes in the United States, where the <code>dab</code> argument is tested and the link disambiguation is adjusted accordingly, as follows:
<syntaxhighlight lang="lua">
AL["US-Bus"] = {
	shield = "US %route%.svg",
	link = "U.S. Route %route% Business ([dab||%dab%, |]Alabama)",
	abbr = "US-%route% Bus.",
	banner = "Business plate.svg",
	width = "expand"
}
</syntaxhighlight>

When parsing the <code>link</code> field, the parser first checks to see if the <code>dab</code> argument was provided. If so, it replaces the statement with <code>%dab%, </code>. If not, the statement is replaced with the empty string placed in the <code>else</code> block. Then, the parser replaces <code>%route%</code> with the route number and, if the <code>dab</code> argument was provided, <code>%dab%</code> with the value of that argument.