# Confusion on \`show\` function in GHCI prompt

**URL:** <https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376>\
**Category:** Learn\
**Created:** [February 10, 2025, 4:40am UTC](https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376 "2025-02-10T04:40:16Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![DendyLiJunyi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/dendylijunyi/32/4945_2.png) [@DendyLiJunyi](https://discourse.haskell.org/u/DendyLiJunyi)\
**Post date:** [February 10, 2025, 4:40am UTC](https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376/1 "2025-02-10T04:40:16Z")

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In the chapter “Higher Order Functions” of the book _Learn You a Haskell For Great Good_, the author wrote "When we type `1 + 1` in the GHCI prompt, then Haskell first calculate `2`, then calls `show` on `2` then print on the screen.

This looks weird because in GHCI prompt I have the following :

```haskell
ghci> 1 + 1
2 

ghci> show 2
"2"

```

If eventually Haskell calls `show` on `2`, why not `1 + 1` returns `"2"`. I try to read the document about `show` but I don’t get many information.

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**Author:** ![rhendric](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/rhendric/32/2689_2.png) [@rhendric](https://discourse.haskell.org/u/rhendric)\
**Post date:** [February 10, 2025, 5:03am UTC](https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376/2 "2025-02-10T05:03:40Z")

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The result of `1 + 1` is the number `2`. A number isn’t a string, and only strings can be written to the screen. Since there are lots of things like numbers that are not strings but that a person might want to look at in GHCi, GHCi will call `show` on anything that it produces for you, whether it’s a string already or not. Then it writes the result of `show` to the screen, which is okay because the result of `show` is always a string!

When you write a string to the screen, it is written verbatim. If your program contains `putStrLn "hello"`, you will see this:

```plaintext
hello

```

So when you type `1 + 1` into GHCi, first it is evaluated to the number `2`. Then GHCi calls `show` on that, giving you the string `"2"`. I have added quotes here because that’s how we talk about strings in Haskell, but they are not part of the string! This is a string that contains only one character: the digit `2`. When GHCi writes the string `"2"` to the screen, all you see is its contents, verbatim, which is the lone digit `2`.

When you type `show 2` into GHCi, first it is evaluated to the string `"2"`. Again I have added quotes here because that is how we talk about strings in Haskell. Then GHCi will call `show` on that, just like it calls `show` on everything it wants to pass back to you. `"2"` is a string already, but that doesn’t matter—you can still call `show` on a string! The result of calling `show` on the one-character string `"2"` is the three-character string `"\"2\""`. Once more, I have added quotes here because that is how we talk about strings in Haskell! When GHCi writes the string `"\"2\""` to the screen, all you see is its contents, verbatim, which are the three characters `"2"`.

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<div class="post-metadata">

**Author:** ![DendyLiJunyi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/dendylijunyi/32/4945_2.png) [@DendyLiJunyi](https://discourse.haskell.org/u/DendyLiJunyi)\
**Post date:** [February 10, 2025, 6:10am UTC](https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376/3 "2025-02-10T06:10:53Z")

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Thank you very much! Now I can see the difference between the two processes.

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**Author:** ![tomjaguarpaw](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/tomjaguarpaw/32/1230_2.png) [@tomjaguarpaw](https://discourse.haskell.org/u/tomjaguarpaw)\
**Post date:** [February 10, 2025, 8:04am UTC](https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376/4 "2025-02-10T08:04:50Z")

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I think you can interpret this as GHCi doing `putStrLn (show _)` of your expression:

```haskell
ghci> 1 + 1
2
ghci> putStrLn (show (1 + 1))
2
ghci> "2"
"2"
ghci> putStrLn (show "2")
"2"

```

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**Author:** ![treblacy](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/treblacy/32/1782_2.png) [@treblacy](https://discourse.haskell.org/u/treblacy)\
**Post date:** [February 10, 2025, 6:08pm UTC](https://discourse.haskell.org/t/confusion-on-show-function-in-ghci-prompt/11376/5 "2025-02-10T18:08:10Z")

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Yeah the book is off by one. It calls `print`, equivalently `putStrLn (show ...)`. It doesn’t just call `show`.