Between

The Between token in RCParsing matches a sequence of three child tokens and propagates the intermediate value of the middle token. It’s optimized for patterns like quoted strings or bracketed expressions.

Overview

The Between token is a specialized sequence that matches a prefix, a main token, and a suffix, but only calculates propagates the main token’s value. This reduces boilerplate compared to a standard Sequence with .Pass(1) or .Pass(v => v[1]).

Example

Here’s an example of parsing a quoted string:

var builder = new ParserBuilder();

builder.CreateToken("string")
    .Between(
        b => b.Literal("\""),
        b => b.EscapedTextPrefix(prefix: '\\', '\\', '\"'),
        b => b.Literal("\"")
    );

var parser = builder.Build();
var result = parser.MatchToken("string", "\"hello\\\"world\"");
var value = result.GetIntermediateValue<string>(); // "hello"world"

Use Cases

• Quoted Strings: Parse strings with delimiters, e.g., "hello".
• Bracketed Expressions: Match content between parentheses or braces.
• Delimited Patterns: Extract content between specific tokens.

Intermediate Values

The Between token automatically propagates the middle child’s intermediate value, while not calculating other children's values:

builder.CreateToken("number")
    .Between(
        b => b.CaptureText(b => b.Literal("(")), // CaptureText will just match child without doing allocations via making substring
        b => b.Number<int>(),                    // Value of this token value will be calculated and propagated
        b => b.CaptureText(b => b.Literal(")"))  // But this will ignored
    );

var parser = builder.Build();
var result = parser.MatchToken("number", "(123)");
var value = result.GetIntermediateValue<int>(); // 123

Notes

• Optimized: More efficient than a Sequence with .Pass(1).
• Three Children: Requires exactly three child tokens.
• No Rules: Tokens cannot reference rules, only other tokens.

Related Tutorials

• First Token
• Second Token
• Sequence Token