Parser

A parser that produces a value of type A.

The context is used to represent the possibility of resuming the parser with additional input and, optionally, already parsed input. There are two context types provided:

• Complete which is the result type for parsers that cannot be resumed.
• Resumable, which is the result type for parsers that can be resumed.

There are three cases within Complete:

• Epsilon, for a parser that failed but did not consume any input;
• Committed, for a parser that failed after consuming some input; and
• Success, for a parser that successfully parsed a portion of it's input and produced a value of type A.

Resumable adds an additional cause for a parser that can be resumed.

Parsers can be resumed if they accept their complete input but do not parse it. In other words, a parser that Committed to its entire input. Additionally, the programmer must indicate that a parser can be resumed using the resumable method.

Resumption is quite limited. The original input is not reparsed on resumption. Parsing starts again on the new input and hence a parser cannot carry state across resumption boundaries.