Second

The Second token in RCParsing matches a sequence of two child tokens and propagates the intermediate value of the second token. It’s optimized for patterns where the second part of a sequence is needed.

Overview

The Second token is a specialized sequence that matches two tokens but only propagates the second token’s value. This is useful for patterns where a suffix or main content follows a prefix.

Example

Here’s an example of parsing an identifier with a suffix:

var builder = new ParserBuilder();

builder.CreateToken("suffixed_identifier")
    .Second(
        b => b.Literal("_"),
        b => b.CaptureText(b => b.Identifier())
    );

var parser = builder.Build();
var result = parser.MatchToken("suffixed_identifier", "_variable");
var value = result.GetIntermediateValue<string>(); // "variable"

Use Cases

• Suffixed Tokens: Match identifiers with suffixes like _id.
• Structured Patterns: Extract the second part of a two-token sequence.
• Simplified Parsing: Avoid manual value propagation.

Intermediate Values

The Second token propagates the second child’s intermediate value:

builder.CreateToken("suffixed_number")
    .Second(
        b => b.Literal("#"),
        b => b.Number<int>()
    );

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

Notes

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

Related Tutorials

• Between Token
• First Token
• Sequence Token