struct Char::Reader

Overview

A Char::Reader allows iterating a String by Chars.

As soon as you instantiate a Char::Reader it will decode the first char in the String, which can be accessed by invoking #current_char. At this point #pos, the current position in the string, will equal zero. Successive calls to #next_char return the next chars in the string, advancing #pos.

Note that the null character '\0' will be returned in #current_char when the end is reached (as well as when the string is empty). Thus, #has_next? will return false only when #pos is equal to the string's bytesize, in which case #current_char will always be '\0'.

Included Modules

Defined in:

char/reader.cr

Constructors

Instance Method Summary

Instance methods inherited from module Enumerable(Char)

accumulate(initial : U) : Array(U) forall U
accumulate : Array(T)
accumulate(initial : U, &block : U, T -> U) : Array(U) forall U
accumulate(&block : T, T -> T) : Array(T) accumulate
, all?(& : T -> ) : Bool
all?(pattern) : Bool
all? : Bool all?
, any?(& : T -> ) : Bool
any?(pattern) : Bool
any? : Bool any?
, chunks(&block : T -> U) forall U chunks, compact_map(& : T -> _) compact_map, count(& : T -> ) : Int32
count(item) : Int32 count
, cycle(n, & : T -> ) : Nil
cycle(& : T -> ) : Nil cycle
, each(& : T -> ) each, each_cons(count : Int, reuse = false, &) each_cons, each_cons_pair(& : T, T -> ) : Nil each_cons_pair, each_slice(count : Int, reuse = false, &) each_slice, each_with_index(offset = 0, &) each_with_index, each_with_object(obj : U, & : T, U -> ) : U forall U each_with_object, empty? : Bool empty?, find(if_none = nil, & : T -> ) find, first(&)
first(count : Int) : Array(T)
first : T first
, first? : T? first?, flat_map(& : T -> _) flat_map, group_by(& : T -> U) forall U group_by, in_groups_of(size : Int, filled_up_with : U = nil) forall U
in_groups_of(size : Int, filled_up_with : U = nil, reuse = false, &) forall U in_groups_of
, includes?(obj) : Bool includes?, index(& : T -> ) : Int32?
index(obj) : Int32? index
, index_by(& : T -> U) : Hash(U, T) forall U index_by, join(io : IO, separator = "") : Nil
join(separator, io : IO) : Nil
join(separator = "") : String
join(io : IO, separator = "", & : T, IO -> )
join(separator, io : IO, &)
join(separator = "", & : T -> ) join
, map(& : T -> U) : Array(U) forall U map, map_with_index(offset = 0, & : T, Int32 -> U) : Array(U) forall U map_with_index, max : T max, max? : T? max?, max_by(& : T -> U) : T forall U max_by, max_by?(& : T -> U) : T? forall U max_by?, max_of(& : T -> U) : U forall U max_of, max_of?(& : T -> U) : U? forall U max_of?, min : T min, min? : T? min?, min_by(& : T -> U) : T forall U min_by, min_by?(& : T -> U) : T? forall U min_by?, min_of(& : T -> U) : U forall U min_of, min_of?(& : T -> U) : U? forall U min_of?, minmax : Tuple(T, T) minmax, minmax? : Tuple(T?, T?) minmax?, minmax_by(& : T -> U) : Tuple(T, T) forall U minmax_by, minmax_by?(& : T -> U) : Tuple(T, T) | Tuple(Nil, Nil) forall U minmax_by?, minmax_of(& : T -> U) : Tuple(U, U) forall U minmax_of, minmax_of?(& : T -> U) : Tuple(U, U) | Tuple(Nil, Nil) forall U minmax_of?, none?(& : T -> ) : Bool
none?(pattern) : Bool
none? : Bool none?
, one?(& : T -> ) : Bool
one?(pattern) : Bool
one? : Bool one?
, partition(& : T -> ) : Tuple(Array(T), Array(T)) partition, product(initial : Number)
product
product(initial : Number, & : T -> )
product(& : T -> _) product
, reduce(memo, &)
reduce(&) reduce
, reduce?(&) reduce?, reject(& : T -> )
reject(type : U.class) forall U
reject(pattern) : Array(T) reject
, sample(n : Int, random = Random::DEFAULT) : Array(T)
sample(random = Random::DEFAULT) : T sample
, select(& : T -> )
select(type : U.class) : Array(U) forall U
select(pattern) : Array(T) select
, size : Int32 size, skip(count : Int) skip, skip_while(& : T -> ) : Array(T) skip_while, sum(initial)
sum
sum(initial, & : T -> )
sum(& : T -> ) sum
, take_while(& : T -> ) : Array(T) take_while, tally : Hash(T, Int32) tally, tally_by(& : T -> U) : Hash(U, Int32) forall U tally_by, to_a to_a, to_h
to_h(& : T -> Tuple(K, V)) forall K, V to_h
, to_set : Set(T) to_set, zip(*others : Indexable | Iterable | Iterator, &)
zip(*others : Indexable | Iterable | Iterator) zip
, zip?(*others : Indexable | Iterable | Iterator, &)
zip?(*others : Indexable | Iterable | Iterator) zip?

Class methods inherited from module Enumerable(Char)

element_type(x) element_type

Instance methods inherited from struct Struct

==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

Instance methods inherited from struct Value

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==
, dup dup

Instance methods inherited from class Object

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===
, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash
, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?
, inspect(io : IO) : Nil
inspect : String inspect
, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json
, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json
, to_s(io : IO) : Nil
to_s : String to_s
, to_yaml(io : IO) : Nil
to_yaml : String to_yaml
, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

Class methods inherited from class Object

from_json(string_or_io, root : String)
from_json(string_or_io) from_json
, from_yaml(string_or_io : String | IO) from_yaml

Constructor Detail

def self.new(string : String, pos = 0)Source

Creates a reader with the specified string positioned at byte index pos.

def self.new(*, at_end string : String)Source

Creates a reader that will be positioned at the last char of the given string.

Instance Method Detail

def current_char : CharSource

Returns the current character.

reader = Char::Reader.new("ab")
reader.current_char # => 'a'
reader.next_char
reader.current_char # => 'b'

def current_char_width : Int32Source

Returns the size of the #current_char (in bytes) as if it were encoded in UTF-8.

reader = Char::Reader.new("aé")
reader.current_char_width # => 1
reader.next_char
reader.current_char_width # => 2

def each(&) : NilSource

Yields successive characters from #string starting from #pos.

reader = Char::Reader.new("abc")
reader.next_char
reader.each do |c|
  puts c.upcase
end
B
C

def error : UInt8?Source

If there was an error decoding the current char because of an invalid UTF-8 byte sequence, returns the byte that produced the invalid encoding. Returns 0 if the char would've been out of bounds. Otherwise returns nil.

def has_next? : BoolSource

Returns true if there is a character left to read. The terminating byte '\0' is considered a valid character by this method.

reader = Char::Reader.new("a")
reader.has_next?      # => true
reader.peek_next_char # => '\0'

def has_previous? : BoolSource

Returns true if there are characters before the current one.

def next_char : CharSource

Reads the next character in the string, #pos is incremented. Raises IndexError if the reader is at the end of the #string.

reader = Char::Reader.new("ab")
reader.next_char # => 'b'

def peek_next_char : CharSource

Returns the next character in the #string without incrementing #pos. Raises IndexError if the reader is at the end of the #string.

reader = Char::Reader.new("ab")
reader.peek_next_char # => 'b'
reader.current_char   # => 'a'

def pos : Int32Source

Returns the position of the current character.

reader = Char::Reader.new("ab")
reader.pos # => 0
reader.next_char
reader.pos # => 1

def pos=(pos)Source

Sets #pos to pos.

reader = Char::Reader.new("abc")
reader.next_char
reader.next_char
reader.pos = 0
reader.current_char # => 'a'

def previous_char : CharSource

Returns the previous character, #pos is decremented. Raises IndexError if the reader is at the beginning of the #string

def string : StringSource

Returns the reader's String.

© 2012–2021 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/1.2.1/Char/Reader.html