String and Character
PHP doesn't have a separate type for strings and characters, as opposed to some languages where string is defined as a list of characters. Still, as a convention in Parsica and its documentation, we generally use
'1' (single quoted) to indicate a single character, and
"abc123" (double quoted) to indicate a string.
We also use single quotes to indicate constant strings or symbols, such as
Predicates are either prefixed with
is or suffixed with
A parser for a single character is always suffixed with
Char, as in
digitChar(). These always output a string.
Some parsers have case-insensitive versions. These are sufficed with 'I'.