Similar function peek( ); (from C++) in Ruby

Question

Is there any similar peek(); (From C++) function in ruby? Any alternative to do this?

I've found a way to do this.

Use the StringScanner:

require 'strscan'
scanner = StringScanner.new(YourStringHere)
puts scanner.peek(1)

You can use the StringScanner to scan files as well:

file = File.open('hello.txt', 'rb')
scanner = StringScanner.new(file.read)

For those unfamiliar with C++, `peek` returns the next character without consuming input. — Pubby, Apr 07 '12 at 03:17

score 2 · Accepted Answer · answered Apr 07 '12 at 03:43

2

Maybe you can use ungetc. Try to look here.

It is not equal but you can obtain the same result.

answered Apr 07 '12 at 03:43

dash1e

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Yes, you can do that. (And remember to accept the answer if it fits your needs :P) – dash1e Apr 07 '12 at 03:54

score 1 · Answer 2 · answered Apr 07 '12 at 16:19

Enumerator#peek let's you peek at the next value of an Enumerator. IO#bytes IO#chars will give you an Enumerator on a byte stream or character stream respectively. Since you opened with "rb", I'll assume you want bytes.

file = File.open('hello.txt', 'rb') # assume contains text "hello\n"
fstream = file.bytes

fstream.next # => "h"
fstream.peek # => "e"
fstream.next # => "e"
...

Of course now you're kinda stuck with byte at a time processing on the stream.

Similar function peek( ); (from C++) in Ruby

2 Answers2