The Amazing Interactive Turing Machine

An interactive fiction by J.D. Clemens (2006) - the Inform 7 source text

Home page

Contents
Previous
Next

Complete text		Section 8 - Stepping

Stepping is an action applying to nothing. Understand "step" as stepping.

Instead of stepping when the machine is active:
    now the machine is paused;
    say "You press the yellow button and the machine pauses."

Check stepping: if the machine is stopped, say "The machine has halted. You will need to reset it before running it again." instead.

Check stepping:
    if there is a StateN of the current state in the Table of State Transitions, continue the action;
    say "The machine has halted." instead.
    
Carry out stepping:
    carry out the single stepping activity.

Report stepping: say "You press the button and the machine grinds [if the current state is the previous state]along[otherwise]into state [current state][end if]. The tape shows: [tape contents]."

Single stepping is an activity.

The last for single stepping rule:
    change previous state to current state;
    if head position > 0, let bit be Symbol in row head position of the Table of Tape Values;
    choose row with a StateN of current state in the Table of State Transitions;
    if head position is 0 begin;
        change the current state to the E State entry;
        change the head position to 1;
    otherwise;
        let new state be the Z State entry;
        let new action be the Z Action entry;
        if bit is 1 begin;
            let new state be the O State entry;
            let new action be the O Action entry;
        end if;
        change the current state to the new state;
        if the new action is move left, decrease the head position by 1;
        if the new action is move right, increase the head position by 1;
        if the head position > the number of rows in the Table of Tape Values begin;
            decrease the head position by 1;
            now the machine is stopped;
            say "There is a terrible wrenching sound as the machine tries to run off the end of the tape and grinds to a halt.";
        end if;
        if the new action is write zero, change the Symbol in row head position of the Table of Tape Values to 0;
        if the new action is write one, change the Symbol in row head position of the Table of Tape Values to 1;
        if the new action is halt, now the machine is stopped;
    end if;
    if there is a StateN of current state in the Table of State Transitions, do nothing;
    otherwise now the machine is stopped;
    now the machine is used.