Obtaining user input

prompt_read(Prompt_list, Term)
ask(Prompt_list,Input)

• Both are modeless dialogs - with an edit field into which the required term is to be entered
• Prompt_list is the sentence displayed within the dialog, and Term is the variable to which the input of the user is bound
• If the user simply presses return - or clicks on the OK button, Term is bound to the built in end_of_file.

read1 :-
  prompt_read(['Enter a likes clause'],Clause).

read2(Name, Feeling) :- 
  ask(['How are you,', Name, ?],Feeling),
  write(Feeling).

  
Figure 1: Prompt dialog

  
Figure 2: Ask dialog

• For the ask dialog, no syntax checks are made on the input
• The Input argument - in the example this is the variable Feeling will be bound to a list of tokens entered in the edit field, hence :

  Feeling =
   ['A', little, dizzy, from, last, night, ',', 
       but,'OK','I',guess]

• This can then be processed by the calling program (as required).

menu(Music) :-
 scroll_menu(['What music do you like ?'],
 ['Pop','Indie','Jazz','Metal','Punk',
 'Fusion','Classical','Reggae','Dance'],
 ['Jazz'], Music).

• Displays a scrolling menu for selecting one or more items
• The menu dialog is modal
• The general form is :

  scroll_menu(Prompt,Menu_list,Preselected,Selected)

• Prompt refers to the question asked from the user, Menu_list corresponds to the different choices offered, Preselected is the item highlighted when the menu is invoked and Selected is a variable containing the choices made by the user
• In the above example, if the user selected Jazz, then

  Music = ['Jazz']

• If multiple options were selected (by holding down the shift key and pressing the mouse button), then

  Music = ['Metal','Punk','Dance']

• If the atom 'Jazz' instead of the list

  ['Jazz']

  was the Preselected argument in the example, then only ONE option would be selectable from the menu list

  
Figure 3: Dialog Menu

• A simple dialog can be used to obtain a yes/no type of response from the user. This is achieved by the use of the modal and modeless yes/no dialog

  yesno(Prompt_list)
  myesno(Prompt_list)

• Prompt_list is a sequence of terms separated by spaces

question1 :-
 yesno(['Is the moon green',?]).

question2 :-
  myesno(['Have you switched off the gas',?]).

  
Figure 4: The Modeless yes/no dialog

  
Figure 5: The Modal yes/no dialog