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<!--Weave of 'S/at2' generated by 7-->
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<ul class="crumbs"><li><a href="../webs.html">★</a></li><li><a href="index.html">standard_rules Template Library</a></li><li><b>Activities Template</b></li></ul><p class="purpose">To run the necessary rulebooks to carry out an activity.</p>
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<ul class="toc"><li><a href="#SP1">§1. The Activities Stack</a></li><li><a href="#SP2">§2. Rule Debugging Inhibition</a></li><li><a href="#SP3">§3. Testing Activities</a></li><li><a href="#SP4">§4. Emptiness</a></li><li><a href="#SP5">§5. Process Activity Rulebook</a></li><li><a href="#SP6">§6. Carrying Out Activities</a></li><li><a href="#SP7">§7. Begin</a></li><li><a href="#SP8">§8. For</a></li><li><a href="#SP9">§9. End</a></li><li><a href="#SP10">§10. Abandon</a></li></ul><hr class="tocbar">
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<p class="inwebparagraph"><a id="SP1"></a><b>§1. The Activities Stack. </b>Activities are more like nested function calls than independent processes;
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they finish in reverse order of starting, and are placed on a stack. This
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needs only very limited size in practice: 20 might seem a bit low, but making
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it much higher simply means that oddball bugs in the user's code — where
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activities recursively cause themselves ad infinitum — will be caught less
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efficiently.
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</p>
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<pre class="display">
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<span class="plain">Constant MAX_NESTED_ACTIVITIES = 20;</span>
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<span class="plain">Global activities_sp = 0;</span>
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<span class="plain">Array activities_stack --> MAX_NESTED_ACTIVITIES;</span>
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<span class="plain">Array activity_parameters_stack --> MAX_NESTED_ACTIVITIES;</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP2"></a><b>§2. Rule Debugging Inhibition. </b>The output from RULES or RULES ALL becomes totally illegible if it is applied
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even to the activities printing names of objects, so this is inhibited when
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any such activity is running. <code class="display"><span class="extract">FixInhibitFlag</span></code> is called each time the stack
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changes and ensures that <code class="display"><span class="extract">inhibit_flag</span></code> has exactly this meaning.
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</p>
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<pre class="display">
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<span class="plain">Global inhibit_flag = 0;</span>
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<span class="plain">Global saved_debug_rules = 0;</span>
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<span class="plain">[ FixInhibitFlag n act inhibit_rule_debugging;</span>
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<span class="plain">for (n=0:n<activities_sp:n++) {</span>
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<span class="plain">act = activities_stack-->n;</span>
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<span class="plain">if (act == PRINTING_THE_NAME_ACT or PRINTING_THE_PLURAL_NAME_ACT or</span>
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<span class="plain">PRINTING_ROOM_DESC_DETAILS_ACT or PRINTING_INVENTORY_DETAILS_ACT or</span>
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<span class="plain">LISTING_CONTENTS_ACT or GROUPING_TOGETHER_ACT or PRINTING_RESPONSE_ACT)</span>
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<span class="plain">inhibit_rule_debugging = true;</span>
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<span class="plain">}</span>
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<span class="plain">if ((inhibit_flag == false) && (inhibit_rule_debugging)) {</span>
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<span class="plain">saved_debug_rules = debug_rules;</span>
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<span class="plain">debug_rules = 0;</span>
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<span class="plain">}</span>
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<span class="plain">if ((inhibit_flag) && (inhibit_rule_debugging == false)) {</span>
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<span class="plain">debug_rules = saved_debug_rules;</span>
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<span class="plain">}</span>
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<span class="plain">inhibit_flag = inhibit_rule_debugging;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP3"></a><b>§3. Testing Activities. </b>The following tests whether a given activity <code class="display"><span class="extract">A</span></code> is currently running
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whose parameter-object matches description <code class="display"><span class="extract">desc</span></code>, where as usual the
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description is represented by a routine testing membership, and where
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zero <code class="display"><span class="extract">desc</span></code> means that any parameter is valid. Alternatively, we can
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require a specific parameter value of <code class="display"><span class="extract">val</span></code>.
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</p>
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<pre class="display">
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<span class="plain">[ TestActivity A desc val i;</span>
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<span class="plain">for (i=0:i<activities_sp:i++)</span>
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<span class="plain">if (activities_stack-->i == A) {</span>
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<span class="plain">if (desc) {</span>
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<span class="plain">if ((desc)(activity_parameters_stack-->i)) rtrue;</span>
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<span class="plain">} else if (val) {</span>
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<span class="plain">if (val == activity_parameters_stack-->i) rtrue;</span>
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<span class="plain">} else rtrue;</span>
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<span class="plain">}</span>
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<span class="plain">rfalse;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP4"></a><b>§4. Emptiness. </b>An activity is defined by its three rulebooks: it is empty if they are all
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empty.
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</p>
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<pre class="display">
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<span class="plain">[ ActivityEmpty A x;</span>
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<span class="plain">x = Activity_before_rulebooks-->A;</span>
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<span class="plain">if (rulebooks_array-->x ~= EMPTY_RULEBOOK) rfalse;</span>
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<span class="plain">x = Activity_for_rulebooks-->A;</span>
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<span class="plain">if (rulebooks_array-->x ~= EMPTY_RULEBOOK) rfalse;</span>
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<span class="plain">x = Activity_after_rulebooks-->A;</span>
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<span class="plain">if (rulebooks_array-->x ~= EMPTY_RULEBOOK) rfalse;</span>
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<span class="plain">rtrue;</span>
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<span class="plain">];</span>
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<span class="plain">[ RulebookEmpty rb;</span>
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<span class="plain">if (rulebooks_array-->rb ~= EMPTY_RULEBOOK) rfalse;</span>
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<span class="plain">rtrue;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP5"></a><b>§5. Process Activity Rulebook. </b>This is really much like processing any rulebook, except that <code class="display"><span class="extract">self</span></code> is
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temporarily set to the parameter, and is preserved by the process.
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</p>
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<pre class="display">
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<span class="plain">[ ProcessActivityRulebook rulebook parameter rv;</span>
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<span class="plain">@push self;</span>
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<span class="plain">if (parameter) self = parameter;</span>
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<span class="plain">rv = FollowRulebook(rulebook, parameter, true);</span>
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<span class="plain">@pull self;</span>
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<span class="plain">if (rv) rtrue;</span>
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<span class="plain">rfalse;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP6"></a><b>§6. Carrying Out Activities. </b>This is a three-stage process; most activities are run by calling the following
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simple routine, but some are run by calling the three subroutines independently.
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</p>
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<pre class="display">
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<span class="plain">[ CarryOutActivity A o rv;</span>
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<span class="plain">BeginActivity(A, o);</span>
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<span class="plain">rv = ForActivity(A, o);</span>
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<span class="plain">EndActivity(A, o);</span>
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<span class="plain">return rv;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP7"></a><b>§7. Begin. </b>Note that when an activity based on the conjectural "future action" is
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being run — in a few parser-related cases, that is — the identity of this
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action is put temporarily into <code class="display"><span class="extract">action</span></code>, and the current value saved while
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this takes place. That allows rules in the activity rulebooks to have
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preambles based on the current action, and yet be tested against what is not
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yet the current action.
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</p>
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<pre class="display">
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<span class="plain">[ BeginActivity A o x;</span>
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<span class="plain">if (activities_sp == MAX_NESTED_ACTIVITIES) return RunTimeProblem(RTP_TOOMANYACTS);</span>
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<span class="plain">activity_parameters_stack-->activities_sp = o;</span>
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<span class="plain">activities_stack-->(activities_sp++) = A;</span>
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<span class="plain">FixInhibitFlag();</span>
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<span class="plain">MStack_CreateAVVars(A);</span>
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<span class="plain">if (Activity_atb_rulebooks->A) { x = action; action = action_to_be; }</span>
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<span class="plain">o = ProcessActivityRulebook(Activity_before_rulebooks-->A, o);</span>
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<span class="plain">if (Activity_atb_rulebooks->A) action = x;</span>
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<span class="plain">return o;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP8"></a><b>§8. For. </b></p>
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<pre class="display">
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<span class="plain">[ ForActivity A o x;</span>
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<span class="plain">if (Activity_atb_rulebooks->A) { x = action; action = action_to_be; }</span>
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<span class="plain">o = ProcessActivityRulebook(Activity_for_rulebooks-->A, o);</span>
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<span class="plain">if (Activity_atb_rulebooks->A) action = x;</span>
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<span class="plain">return o;</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP9"></a><b>§9. End. </b></p>
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<pre class="display">
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<span class="plain">[ EndActivity A o rv x;</span>
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<span class="plain">if ((activities_sp > 0) && (activities_stack-->(activities_sp-1) == A)) {</span>
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<span class="plain">if (Activity_atb_rulebooks->A) { x = action; action = action_to_be; }</span>
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<span class="plain">rv = ProcessActivityRulebook(Activity_after_rulebooks-->A, o);</span>
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<span class="plain">if (Activity_atb_rulebooks->A) action = x;</span>
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<span class="plain">activities_sp--; FixInhibitFlag();</span>
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<span class="plain">MStack_DestroyAVVars(A);</span>
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<span class="plain">return rv;</span>
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<span class="plain">}</span>
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<span class="plain">return RunTimeProblem(RTP_CANTABANDON);</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="inwebparagraph"><a id="SP10"></a><b>§10. Abandon. </b>For (very) rare cases where an activity must be abandoned midway; such an
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activity must be being run by calling the three stages individually, and
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<code class="display"><span class="extract">EndActivity</span></code> must not have been called yet.
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</p>
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<pre class="display">
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<span class="plain">[ AbandonActivity A o;</span>
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<span class="plain">if ((activities_sp > 0) && (activities_stack-->(activities_sp-1) == A)) {</span>
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<span class="plain">activities_sp--; FixInhibitFlag();</span>
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<span class="plain">MStack_DestroyAVVars(A);</span>
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<span class="plain">return;</span>
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<span class="plain">}</span>
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<span class="plain">return RunTimeProblem(RTP_CANTEND);</span>
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<span class="plain">];</span>
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</pre>
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<p class="inwebparagraph"></p>
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<hr class="tocbar">
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<ul class="toc"><li><a href="S-at.html">Back to 'Actions Template'</a></li><li><a href="S-ct.html">Continue with 'Chronology Template'</a></li></ul><hr class="tocbar">
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<!--End of weave-->
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