27.5.5 Specifying substrings in expressions

You can determine the number of characters in a macro variable, and use string operators to extract substrings from the value of the variable. Table 27-7 lists several of the string operators and shows how they are used in macro expressions.

See also:

§27.5.2 Understanding operands and operators

Table 27-4 Operators for HTML macro expressions

Table 27-7 String operators in macro expressions

Operator	Macro expression	Result of expression
		Type	Value
length	($$string length)	Integer	Number of characters in $$string
char	($$string char N)	String	Nth character in $$string, counting from the left; the leftmost character is number 1
first	($$string first N)	String	First N characters of $$string
last	($$string last N)	String	Last N characters of $$string
before	($$string before $$str)	String	Substring that precedes the first (leftmost) occurrence of $$str in $$string
after	($$string after $$str)	String	Substring that follows the first (leftmost) occurrence of $$str in $$string
starts	($$string starts $$str)	Boolean	True if $$str is at the start of $$string
ends	($$string ends $$str)	Boolean	True if $$str is at the end of $$string
contains	($$string contains $$str)	Boolean	True if $$str occurs anywhere in $$string
trim first	($$string trim first N)	String	All but the first N characters of $$string
trim last	($$string trim last N)	String	All but the last N characters of $$string

For example, to trim off the first four characters of $$mystring:

<$$mystring = ($$yourstring trim first 4)>

If the value of $$yourstring is "makework", the value of $$mystring would be "work".

Implied value of second operand

If the second operand N is missing from an expression that uses one of the following operators, a value of 1 (one) is assumed for N:

char

first

last

trim first

trim last

For example, to select only the last character, you can omit the second operand:

<$$yourstring = ($$mystring last)>

If the value of $$mystring is "groceries", the value of $$yourstring would be "s".

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