LiteralChoice

The LiteralChoice token in RCParsing matches one of several specified strings, using a trie for efficient matching. It’s ideal for parsing multiple possible literals, such as keywords.

Overview

The LiteralChoice token tries to match one of a set of strings, selecting the longest match by default. It produces the matched construction-specified string as its intermediate value.

Example

Here’s an example of matching multiple keywords:

var builder = new ParserBuilder();

builder.CreateToken("keyword")
    .LiteralChoice("if", "e", "else", "while");

var parser = builder.Build();
var result = parser.MatchToken("keyword", "else");
var value = result.GetIntermediateValue<string>(); // "else"

With case-insensitive matching:

builder.CreateToken("keyword")
    .LiteralChoice(new[] { "if", "else", "while" }, StringComparer.OrdinalIgnoreCase);

builder.CreateToken("another_keyword")
    .LiteralChoiceIgnoreCase("if", "else", "while");

var parser = builder.Build();
var result1 = parser.MatchToken("keyword", "ELSE");
var result2 = parser.MatchToken("another_keyword", "WHile");
var value1 = result.GetIntermediateValue<string>(); // "else"
var value2 = result.GetIntermediateValue<string>(); // "while"

Use Cases

• Multiple Keywords: Match a set of keywords efficiently.
• Literal Sets: Parse one of several fixed strings.
• Efficient Matching: Use a trie for fast lookup of multiple literals.

Intermediate Values

The LiteralChoice token produces the matched construction-specified string as its intermediate value:

builder.CreateToken("operator")
    .LiteralChoice("+", "-", "*");

var parser = builder.Build();
var result = parser.ParseRule("operator", "*");
var value = result.GetIntermediateValue<string>(); // "*"

Notes

• Trie-Based: Uses a trie for efficient matching of multiple strings.
• Case Sensitivity: Use StringComparer for case-insensitive matching.

Related Tutorials

• Literal Token
• LiteralChar Token
• KeywordChoice Token