Sequence

The Sequence token in RCParsing matches a series of child tokens in a specific order, failing if any child fails. It’s used to define composite token patterns, such as quoted strings or complex literals.

Overview

A Sequence token is created when multiple child tokens are added to a token definition. It ensures that the input matches each child token in order, producing an intermediate value based on the Pass combinator or child values.

Example

Here’s an example of a Sequence token for parsing a quoted string:

var builder = new ParserBuilder();

builder.CreateToken("string")
    .Literal("\"")
    .EscapedTextPrefix(prefix: '\\', '\\', '\"')
    .Literal("\"")
    .Pass(1); // Propagate the EscapedTextPrefix value

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".
• Structured Tokens: Combine multiple tokens into a single unit.

Intermediate Values

The Sequence token propagates the intermediate value of one of its children using .Pass(index) or a custom passage function:

builder.CreateToken("version")
    .Literal("v")
    .Number<int>()
    .Pass(v => v[1]); // Propagate the number's value

var parser = builder.Build();
var result = parser.MatchToken("version", "v123");
var value = result.GetIntermediateValue<int>(); // 123

Notes

• Automatic Creation: Adding multiple tokens implicitly creates a Sequence.
• Pass Combinator: Use .Pass() to control which child’s value is propagated.
• No Rules: Tokens cannot reference rules, only other tokens.

Related Tutorials

• Choice Token
• Optional Token
• Between Token