Convert the first character to uppercase/capital letter using yasnippet

Question

Q: I have the following Yasnippet, which looks like this:

 MYNAME - $1 (`(insert-mode-description)`).
 $2

When I insert the snippet, the cursor starts on $1. Then I begin with typing. I would like to convert the first character of the sentence that I'm typing to uppercase.

When I look in the documentation of Yasnippet, there is a transformer that converts your text to uppercase. I need only to capitalize the first character.

Then I figured out another option:

MYNAME - $1 $2 (`(insert-mode-description)`).
$3

So Everything in $1-place gets converted to uppercase. Then press tab, to jump to $2 and typing further in lowercase letters. But I'm not looking for that. Then I need to press tab every time after I insert the first character. I would just convert the first character of $1 to be uppercase. Any suggestion?

Answer 1

Function to capitalize only the first char

Make sure that the below function is evaluated in your emacs config before the yasnippet snippets are loaded.

(defun my/capitalize-first-char (&optional string)
  "Capitalize only the first character of the input STRING."
  (when (and string (> (length string) 0))
    (let ((first-char (substring string nil 1))
          (rest-str   (substring string 1)))
      (concat (capitalize first-char) rest-str))))

---

Snippet

Here is a snippet that makes use of the above function

# -*- mode: snippet -*-
# name: intro
# key: zname
# --
Hi, my name is ${1:$$(my/capitalize-first-char yas-text)}.
$0

---

Demo

Reference

Answer 2

You may find a working solution here.

Function

(defun capitalizeFirst (s)
  (if (> (length s) 0)
      (concat (upcase (substring s 0 1)) (downcase (substring s 1)))
    nil))

Again put this function to your .emacs file before yasnippet initialization.

Snippet

# -*- mode: snippet -*-
# name: name
# key: name
# --
Hi, my name is ${1:$$(capitalizeFirst yas-text)}

Also some countries use different locales. According to Turkish locale if you convert ırak word which means far, distant to uppercase it should be converted like this Irak.

Here is a function which converts the first character of a string uppercase correctly according to Turkish locale.

Function which converts first character according to Turkish locale

(defun buyukHarfYap (metin)
  (let (ilkHarf sesliMi)
    (if (> (length metin) 0)
        (progn

          (setq ilkHarf (aref metin 0))

          (if (eq ilkHarf 105) ; i harfi
              (aset metin 0 ?İ))

          (if (eq ilkHarf 305) ; ı harfi
              (aset metin 0 ?I))

          (if (eq ilkHarf 97)  ; a harfi
              (aset metin 0 ?A))

          (if (eq ilkHarf 101) ; e harfi
              (aset metin 0 ?E))

          (if (eq ilkHarf 252) ; ü harfi
              (aset metin 0 ?Ü))

          (if (eq ilkHarf 111) ; o harfi
              (aset metin 0 ?O))

          (if (eq ilkHarf 246)
              (aset metin 0 ?Ö)); ö harfi

          (if (eq ilkHarf 117)
              (aset metin 0 ?U)); u harfi

          (setq ilkHarf (substring metin 0 1))

          (setq sesliMi (string-match ilkHarf "AEIİOÖUÜ"))

          (if (eq sesliMi nil)
              (concat (upcase(substring metin 0 1))  (downcase (substring metin 1)))
            (concat (substring metin 0 1)  (downcase (substring metin 1)))))nil)))

Answer 3

Regarding the capitalization part, you can also use s-capitalized-words of the s.el library, which is a handy string library.