alt Hacker NewsCombinators are functional—they always return something. But if you want to return nothing, fine; T is any type. Just return something like unit (ie, the singleton type that has nothing as a value).
Replies
pyrale • today at 11:24 AM
T is not any type, T is a type defined at compile time, and usually checked against the parser’s implementation.
If you always define T as some useful stuff or unit, your experience with parser combinators and their composition is going to be miserable.
➕ show 1 reply
codebje • today at 12:07 PM
A parser for a thing
Is a function from a string
To a list of pairs
Of strings and things.➕ show 1 reply
rdevilla • today at 11:08 AM
[dead]
There are three return states that a parser (or partial parser) can return:
1. an item (`T`) for a successful parse;
2. an error (`ParseError`) for an unrecoverable parse error;
3. a partial item (`T with ParseError`) for a recoverable parse error or warning (known statically).
You may also want to differentiate between:
1. leaf nodes (numbers, identifiers, string literals, etc.);
2. composite/nested nodes (addition, multiplication, variable assignment, etc.).