player stutters when moving.

[Mailman]

So I have my movement code working, but there is always a lag between when I press the button, and when the player starts walking. I have no idea why this happens. This isn't my biggest issue, it's just really confusing.
All my directions are the same, so I'm simply posting the minimal ammount of code I can.

EDIT: I solved my own problem. I only half wrote this code, and forgot to make my inputs Boolean. I COMPLETELY forgot to read the document I wrote to myself and ended up finding it in my google docs when I went to turn something into school.

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   void changePosX(float delta, bool isNegative)
      {
         if (!isNegative)
         {
            playerSprite.move(speed * delta, 0.0f);
         }
         else
         {
            playerSprite.move(-(speed * delta), 0.0f);
         }
      }

Where delta comes from:

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if (sf::Keyboard::isKeyPressed(sf::Keyboard::W))
            {
               
               player.changeDir(player.UP);
               if (player.getPosY() >= 0)
               {
                  player.changePosY(delta, 1);
               }
               
            }