Stack Overflow
Stack Overflow

Questions tagged [peek]

Refers to a non-destructive operation performed on sequential, collection-like data structures that have the notion of "top element" or "next element", such as stacks, queues and streams. The `peek` operation returns the value of the "top" (or "next") element without "consuming" that element, i.e. without removing that element from the data structure.

163 questions
13
votes
1 answer

C++ fstream function that reads a line without extracting?

In C++, is there a function in the fstream library (or any library) that allows me to read a line to a delimiter of '\n' without extracting? I know the peek() function allows the program to 'peek' at the next character its reading in without…
SexyBeastFarEast
  • 143
  • 1
  • 1
  • 7
11
votes
1 answer

How to correctly use `peek()` in Rust?

I am trying to do something simple. In a slice of u8, I want to find occurrence of two characters "\r\n". However, I cannot convert that slice into String using from_utf8 because parts of slice after "\r\n" may not be utf-8 and as far as possible I…
gabhijit
  • 3,345
  • 2
  • 23
  • 36
10
votes
1 answer

Python: why does peek(1) return 8K bytes instead of 1 byte?

I'm using Python 3, and the peek() method for buffered file I/O doesn't seem to work as documented. For example, the following code illustrates the problem -- it prints 8192 as the length of the byte string returned by f.peek(1): jpg_file =…
Doug Mahugh
  • 624
  • 6
  • 15
9
votes
2 answers

Help: ZX81 'BASIC' Peek function

I need a way to find if the character ('<') has hit a wall (Black pixel Graphic) -On a ZX81 game. I'm been looking at another game... which uses code if peek(peek 16398 +256*peek 16399) = code "blackpixel graphic" then ... Which seems to work for…
James Andrew
  • 7,197
  • 14
  • 46
  • 62
9
votes
6 answers

Why is Stack.Peek() a method?

As in the title. Why does the Stack class need a method to return a reference of the top object? I've always been told, that methods suggest there's some computing involved and that simple objects should be returned with properties instead. Peek()…
Tarec
  • 3,268
  • 4
  • 30
  • 47
9
votes
3 answers

Is it possible to Peek below the surface of a Stack?

Is it possible to Peek at the value of a C# Stack variable layers below the surface? In my example, I need to Peek at the value one below. I could Peek to record the value into a temporary variable, Pop and read, then Push the temporary values back,…
Keavon
  • 6,837
  • 9
  • 51
  • 79
8
votes
1 answer

How to properly use cin.peek()

This function is supposed to read a fraction and place it in an array. If the user enters '0' the function is supposed to exit. I am trying to do this using the cin.peek() function but execution always goes into the if statement and doesn't allow…
Zzz
  • 2,927
  • 5
  • 36
  • 58
8
votes
7 answers

pop and peek doing same in that case?

From all the sources I've read, they say - the difference between peek and pop is that peek doesn't remove the top value. In the provided example from my lecture notes, apparently they do the same using a different method of subtraction. After both…
Peter Cerba
  • 806
  • 4
  • 14
  • 26
7
votes
2 answers

peek() Multiple Places Ahead?

Lets say I have an outer while loop to read each character and output it to console. I also want to flag a word if it is found and by using the peek method I can find the first instance of a word. Is there a way to peek multiple places ahead. For…
domonica
  • 526
  • 7
  • 14
7
votes
1 answer

python2.7 peek at stdin

I would like to call sys.stdin.readlines() without removing anything from stdin. I am using Python2.7 on Linux. For example, what I want is: x = sys.stdin.readlines() y = sys.stdin.readlines() then x and y have identical strings. It would be…
Aaron
  • 2,344
  • 3
  • 26
  • 32
7
votes
3 answers

Groovy 'Peeking' ahead with an iterator?

I have various scenarios in loops where I would 'peek' or 'skip' ahead while iterating through items for processing. One scenario is I'm enumerating through lines of a file, and there is a 'continuation' character at the end of a line indicating…
MarkE
  • 123
  • 8
6
votes
2 answers

How to peek on channels without blocking and still being able to detect hangup?

According to the doc of .try_iter() method of the Receiver end of a Rust std::mpsc::channel, I understand that this iterator either yield "None": when there is no data in the channel or when the other end of the channel has hung up. In my case, I…
iago-lito
  • 3,098
  • 3
  • 29
  • 54
6
votes
3 answers

Peeking at a UDP message in c++

I'm trying to receive a UDP message using sockets in c++. I'm sending the size of the message in the header, so I can know how much memory should I allocate, so I try to peek at the beggining of the message like this: int bytesRead =…
Idov
  • 5,006
  • 17
  • 69
  • 106
6
votes
2 answers

Does JMS have a concept of a queue peek?

From a general Computer Science perspective - when we think of a Queue in a logical sense - we think of being able to 'peek' the first item in the queue. When I look at the JMS API - it has a MessageListener - which has an OnMessage() method. This…
hawkeye
  • 34,745
  • 30
  • 150
  • 304
5
votes
5 answers

C#: Using StreamReader to read line from txt file, but Peek() return -1 even there are a lot of lines left

I use Peek() method of StreamReader to check whether there are more lines need to be processed. There are more than 1000 lines in my file, but Peek() suddenly return -1 when it reachs line#750. I checked but seems no differences between line#750 and…
Alan
  • 93
  • 1
  • 2
  • 5
1
2
3
…
10 11