Choose add premise from the proof menu if you are

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Unformatted text preview: als of the proof, which of course is not permitted in solving the exercises. (The Grade Grinder always checks to make sure that no changes have been made to the premises or goals of a proof.) Author mode is used for creating new exercises, and so new 44 / LPL Software Manual files are always opened in author mode. This mode allows you to enter premises into the proof, add goals to the proof, and specify any constraints that apply to the goals. You can tell which mode you are in by looking at Author Mode on the Edit menu. If there is a check in front of Author Mode, Fitch is in author mode; otherwise, it is in user mode. Choosing Author Mode will toggle between these two modes. The current mode is saved with the file, so if you create a new problem, you should turn off author mode before saving it. Alternatively, you can use Save As Problem. . . from the File menu. This command is available only in Author Mode, and will save only the premises and goals in the new file. The created file is saved in user mode. 4.6.1 Adding and deleting premises To add a premise, you must be in Author Mode. Choose Add Premise from the Proof menu. If you are currently focused on a premise step, the new premise will appear immediately after the focused step. If you are focused on a step in the body of the proof, the new premise will appear at the end of the list of premises. To delete a premise, focus on its step and choose Delete Step from the Proof menu. 4.6.2 Adding and deleting goals To add a goal to a problem, choose New Goal from the Goal menu and enter the goal sentence you want. As noted above, this can only be done in Author Mode. To delete a goal from a problem, click on the goal in the goal strip and choose Delete Goal from the Goal menu. You can check use the Check Goal Forms from the Goal menu to check that the goal formulas are well formed. Goals that are not well formed will be marked with a star. If you want to modify the constraints on a goal, choose Edit Goal Constraints from the Goal menu. When you initially add a goal, Fitch assumes that you want the goal to be proven using just the introduction and elimination rules of F . If you want to allow the use of the Con procedures, or if you want to disallow the use of any standard rules, you will have to modify the constraints Using Fitch / 45 Figure 4.3: Fitch Preferences Dialog associated with the goal. Constraints are associated with individual goals, so a problem can have different constraints for different goals. 4.6.3 Saving new problems To save a newly created file as an exercise to be solved, choose Save As Problem. . . from the File menu. This saves the file, but also turns on User Mode in the file, so that users will not accidentally change the premises or goals of the exercise. 4.7 Preferences Some aspects of the behavior of Fitch can be controlled using the preferences dialog. This can be accessed by choosing the Preferences... command from the application menu (Edit Menu on Windows). The preferences dialog is shown in figure 4.3. The preferences allow you to control the style of text for sen...
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This document was uploaded on 01/26/2014.

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