class Fexpr::Scanner

• Fexpr::Scanner
• Reference
• Object

Overview

Reads and tokenizes filter expression text into a stream of tokens.

The scanner processes input character by character, recognizing tokens like:

• Identifiers (e.g., name, age, @timestamp)
• Numbers (e.g., 42, -1.5)
• Quoted text (e.g., "crystal", 'v1.0')
• Operators (e.g., =, !=, &&, ||)
• Groups (expressions in parentheses)
• Comments (starting with //)

Defined in:

fexpr/scanner.cr

Constant Summary

IDENTIFIER_REGEX = /^[\@\#\_]?[\w\.\:]*\w+$/

Regular expression for a valid identifier.

Constructors

• .new(io : IO)

  Creates a new scanner that reads from the given IO.

Instance Method Summary

• #comment_start_char?(ch : Char) : Bool

  Checks if a character is a valid start of a comment.

• #digit_char?(ch : Char) : Bool

  Checks if a character is a digit.

• #group_start_char?(ch : Char) : Bool

  Checks if a character is a valid start of a group/parenthesis.

• #identifier?(literal : String) : Bool

  Checks if a literal is a properly formatted identifier.

• #identifier_start_char?(ch : Char) : Bool

  Checks if a character is a valid first character of an identifier.

• #join_start_char?(ch : Char) : Bool

  Checks if a character is a valid start of a join type operator.

• #letter_char?(ch : Char) : Bool

  Checks if a character is a letter.

• #number?(literal : String) : Bool

  Checks if a literal is numeric.

• #number_start_char?(ch : Char) : Bool

  Checks if a character is a valid first character of a number.

• #reader : IO
• #scan : TokenResult

  Returns the next token from the input stream.

• #sign_start_char?(ch : Char) : Bool

  Checks if a character is a valid start of a sign operator.

• #text_start_char?(ch : Char) : Bool

  Checks if a character is a valid first character of a quoted text.

• #whitespace_char?(ch : Char) : Bool

  Checks if a character is a space, tab, or newline.

Constructor Detail

Instance Method Detail