Repeat

The Repeat token in RCParsing matches a child token a specified number of times within a given range. It fails if the child does not match at least the minimum number of times.

Overview

A Repeat token allows you to specify a minimum and optional maximum number of timesA股 a child token should match. Variants like ZeroOrMore and OneOrMore simplify common cases.

Example

Here’s an example of a Repeat token for parsing multiple digits:

var builder = new ParserBuilder();

builder.CreateToken("digits")
    .Repeat(b => b.Char(c => char.IsDigit(c)), min: 1, max: 3);

var parser = builder.Build();
var result = parser.MatchToken("digits", "123"); // Matches "123"

Using OneOrMore:

builder.CreateToken("digits")
    .OneOrMore(b => b.Char(char.IsDigit));

var parser = builder.Build();
var result = parser.MatchToken("digits", "12345"); // Matches "12345"

Use Cases

• Digit Sequences: Parse sequences of digits or characters.
• Repeated Patterns: Match repeated tokens like keywords or symbols.
• Token Lists: Build lists of simple tokens.

Intermediate Values

The Repeat token produces an array of the children’s intermediate values, which can be customized with .Pass:

builder.CreateToken("digits")
    .OneOrMore(b => b.CaptureText(b => b.Char(char.IsDigit)))
    .Pass(v => v.Cast<string>().ToArray());

var parser = builder.Build();
var result = parser.MatchToken("digits", "123");
var digits = result.GetIntermediateValue<string[]>(); // ["1", "2", "3"]

Notes

• Range Specification: Use min and max to control repetitions.
• Variants: ZeroOrMore (0 or more) and OneOrMore (1 or more) are shortcuts.
• No Rules: Tokens cannot reference rules, only other tokens.

Related Tutorials

• SeparatedRepeat Token
• Sequence Token
• Optional Token