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{{Classic bug
|id=GE-BUG-031
|affected=Classic 3.2e and published classic source
|status=Verified in source
|fixed=ge-next 0.1
|source=Mismatch between three-character command dispatch and exact BUY test
}}

== Summary ==
Classic GE recognizes game commands by their first three characters, but the shared BUY/PRICE transaction routine later tests for the exact word <code>buy</code>. A command token that begins with <code>buy</code> but contains additional characters is dispatched as BUY, then handled as PRICE.

For example:

<syntaxhighlight lang="text">
BUYTHIS 1 TOR
</syntaxhighlight>

displays the price of one torpedo instead of buying it.

== Command dispatch ==
The main command table contains separate three-character entries for BUY and PRICE:

<syntaxhighlight lang="c">
{"buy", cmd_buy, 0},
{"pri", cmd_price, 0},
</syntaxhighlight>

Classic's <code>gesearch()</code> compares only the first three characters of the player's command token:

<syntaxhighlight lang="c">
c = strncmp(ptr, md->command, 3);
</syntaxhighlight>

This is normal GE command behavior. <code>buy</code>, <code>buying</code>, and <code>buythis</code> all begin with the registered command prefix and therefore all dispatch to <code>cmd_buy()</code>.

== Shared BUY and PRICE logic ==
<code>cmd_buy()</code> and <code>cmd_price()</code> perform their command-specific checks, identify the requested item, and then call the same unfortunately named <code>buy(item)</code> worker. That worker calculates availability and price for both commands.

It decides whether to execute a purchase or merely display the price with this test:

<syntaxhighlight lang="c">
if (sameas(margv[0], "buy"))
{
/* transfer the item and charge the player */
}
else
{
/* print PRICE1 */
}
</syntaxhighlight>

Unlike <code>gesearch()</code>, <code>sameas()</code> requires the complete strings to match. A token such as <code>buythis</code> has already passed BUY dispatch, but it fails this exact comparison and falls into the PRICE branch.

== Gameplay consequences ==
The command does not remove cash, transfer stock, or complete a purchase. It only reports what the transaction would cost. This is not normally destructive, but it is inconsistent with the parser rules used by every game command and can be confusing when a typo or habitual long form otherwise appears to have been accepted.

The bug is particularly unobvious because:

* the command is not rejected as invalid;
* BUY syntax and item validation have already succeeded;
* the resulting price message is plausible; and
* entering exactly <code>buy</code> immediately makes the transaction work.

PRICE itself behaves as intended. Tokens beginning with <code>pri</code> reach <code>cmd_price()</code> and correctly take the non-BUY branch in the shared worker.

== Correction in ge-next ==
ge-next 0.1 changed the shared worker to use the same prefix rule as the command dispatcher:

<syntaxhighlight lang="c">
if (strncmp(margv[0], "buy", 3) == 0)
{
/* complete purchase */
}
else
{
/* display price */
}
</syntaxhighlight>

Any token that the command table accepts as BUY is therefore treated as BUY by the transaction routine. PRICE continues to use the same worker without being mistaken for a purchase.

An alternative structural correction would pass an explicit buy-or-price flag to the worker or use separate workers. The three-character comparison was the smallest change and preserves classic GE's established command-prefix behavior.

[[Category:Classic bugs: Commands]]
[[Category:Classic bugs: Economy]]

{{GE navigation}}

Classic bug: Extended BUY token executes PRICE - Revision history

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