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 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'.

NOTE For performance reasons, Char::Reader has value semantics, so care must be taken when a reader is declared as a local variable and passed to another method:

def lstrip(reader)
  until reader.current_char.whitespace?
    reader.next_char
  end
  reader
end

# caller's internal state is untouched
reader = Char::Reader.new("   abc")
lstrip(reader)
reader.current_char # => ' '

# to modify caller's internal state, the method must return a new reader
reader = lstrip(reader)
reader.current_char # => 'a'

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_step(n : Int, *, offset : Int = 0, & : T -> ) : Nil each_step, 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, find!(& : T -> ) : T find!, first(&)
first(count : Int) : Array(T)
first : T
first
, first? : T | Nil 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
, in_slices_of(size : Int) : Array(Array(T)) in_slices_of, includes?(obj) : Bool includes?, index(& : T -> ) : Int32 | Nil
index(obj) : Int32 | Nil
index
, 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(count : Int) : Array(T)
max : T
max
, max? : T | Nil max?, max_by(& : T -> U) : T forall U max_by, max_by?(& : T -> U) : T | Nil forall U max_by?, max_of(& : T -> U) : U forall U max_of, max_of?(& : T -> U) : U | Nil forall U max_of?, min(count : Int) : Array(T)
min : T
min
, min? : T | Nil min?, min_by(& : T -> U) : T forall U min_by, min_by?(& : T -> U) : T | Nil forall U min_by?, min_of(& : T -> U) : U forall U min_of, min_of?(& : T -> U) : U | Nil forall U min_of?, minmax : Tuple(T, T) minmax, minmax? : Tuple(T | Nil, T | Nil) 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(type : U.class) forall U
partition
, present? : Bool present?, 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 = Random::DEFAULT) : Array(T)
sample(random : 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)
tally : Hash(T, Int32)
tally
, tally_by(hash, &)
tally_by(&block : T -> U) : Hash(U, Int32) forall U
tally_by
, to_a : Array(T)
to_a(& : T -> U) : Array(U) forall U
to_a
, to_h
to_h(& : T -> Tuple(K, V)) forall K, V
to_h
, to_set : Set(T)
to_set(&block : T -> U) : Set(U) forall U
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!(message)
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

Macros inherited from class Object

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

Constructor Detail

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

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


[View source]
def self.new(*, at_end string : String) #

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


[View source]

Instance Method Detail

def current_char : Char #

Returns the current character, or '\0' if the reader is at the end of the string.

reader = Char::Reader.new("ab")
reader.current_char # => 'a'
reader.next_char
reader.current_char # => 'b'
reader.next_char
reader.current_char # => '\0'

[View source]
def current_char? : Char | Nil #

Returns the current character.

Returns nil if the reader is at the end of the string.


[View source]
def current_char_width : Int32 #

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

[View source]
def each(&) : Nil #

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

[View source]
def error : UInt8 | Nil #

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.


[View source]
def has_next? : Bool #

Returns true if the reader is not at the end of the string.

NOTE This only means #next_char will successfully increment #pos; if the reader is already at the last character, #next_char will return the terminating null byte because there isn't really a next character.

reader = Char::Reader.new("ab")
reader.has_next? # => true
reader.next_char # => 'b'
reader.has_next? # => true
reader.next_char # => '\0'
reader.has_next? # => false

[View source]
def has_previous? : Bool #

Returns true if the reader is not at the beginning of the string.


[View source]
def next_char : Char #

Reads the next character in the string.

If the reader is at the end of the string after incrementing #pos, returns '\0'. If the reader is already at the end beforehand, raises IndexError.

reader = Char::Reader.new("abc")
reader.next_char # => 'b'
reader.next_char # => 'c'
reader.next_char # => '\0'
reader.next_char # raise IndexError

[View source]
def next_char? : Char | Nil #

Tries to read the next character in the string.

If the reader is at the end of the string before or after incrementing #pos, returns nil.

reader = Char::Reader.new("abc")
reader.next_char?   # => 'b'
reader.next_char?   # => 'c'
reader.next_char?   # => nil
reader.current_char # => '\0'

[View source]
def peek_next_char : Char #

Returns the next character in the #string without incrementing #pos.

Returns '\0' if the reader is at the last character of the string. Raises IndexError if the reader is at the end.

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

[View source]
def pos : Int32 #

Returns the byte position of the current character.

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

[View source]
def pos=(pos : Int32) #

Sets #pos to pos.

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

[View source]
def previous_char : Char #

Reads the previous character in the string.

Raises IndexError if the reader is already at the beginning of the string. Otherwise decrements #pos.

reader = Char::Reader.new(at_end: "abc")
reader.previous_char # => 'b'
reader.previous_char # => 'a'
reader.previous_char # raises IndexError

[View source]
def previous_char? : Char | Nil #

Tries to read the previous character in the string.

Returns nil if the reader is already at the beginning of the string. Otherwise decrements #pos.

reader = Char::Reader.new(at_end: "abc")
reader.previous_char? # => 'b'
reader.previous_char? # => 'a'
reader.previous_char? # => nil

[View source]
def string : String #

Returns the reader's String.


[View source]