Landon Curt Noll
f29b37e49a
Prepare for the winners of **IOCCC28**. > However these are not the 2024 droids you are looking for. :-) The HTML menu (both JavaScript and non-JavaScript) has been updated. The `Status -> Rules and guidelines' have been replaced with two separate menus `Status -> IOCCC rules` and `Status -> IOCCC guidelines`. Added a new top level `social.html` page: built from a new `social.md`. Sorted rules for building specific web pages in the top level `Makefile`. Added `make social` to make the `social.html` page from `social.md`. The `bin/gen-top-html.sh` now is able to process a argument of **social** to process the new top level `social.html` page. Changed `bin/gen-top-html.sh` VERSION from "2.0.0 2025-03-13" to "2.0.1 2025-07-25". Below `About -> Home page` a new `About -> IOCCC social media` menu item as added. Because the menu change touched every HTML file, we changed the general copyright date range for HTML files from "1984-2024" to "1984-2025" due to the extensive changes made for **IOCCC28**. Those markdown files that were modified in 2025 had their copyright date range also changed from "1984-2024" to "1984-2025". Rebuilt tarballs and sitemap due to the extensive HTML rebuilding. Ran `make update` to perform the above.
To build:
make
To use:
./hou 'expression'
Try:
./try.sh
As the script asks you, what does the last one mean? Can you get it to report a different value? Hint: it's in this file, kind of.
Judges' remarks:
This self-documenting scientific calculator compiles clean with no warnings under the most strict pedantic mode of gcc and clang.
The first example, along with the correct result appears in the source code. What does it mean?
The calculator obeys the precedence rules and allows parenthesis.
./hou '1+2*3'
./hou '(1+2)*3'
What exactly does the text formatting do?
What does this evaluate to in C?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
Self documenting source
Comments would almost be redundant. :-}
The ASCII art is valid C code
... and not just fancy formatted comment removed by the C Pre-processor.
The only multi-byte strings are format strings
The code does not contain some simple string-encoded lookup table for calculator operations.
Example input and output in the source
The example input and output in the C code is significant. Can you find out why?
The button layout
The button layout in the C code is significant ... not just a nice looking layout.
Input parsing
The parser is functionally equivalent to a normal arithmetic parser for all valid inputs. For another fun challenge: try to determine how it parses the command line argument.
Author's remarks:
Obfuscations
This program is designed to be self-documenting. It doesn't just provide an example command line. It also provides the expected output and illustrates all supported functionality using embedded ASCII art.
- A few line numbers are significant and careless beautification will break the program.
- The entire ASCII art is valid code. The preprocessor won't remove any part of it.
- The only strings longer than 1 byte are
printf(3)/sscanf(3)format strings, even after preprocessing. No string-encoded lookup table is used. - The example input and its expected output are both algorithmically significant.
- The button layout is also significant.
- The actual syntax being parsed is not that obvious, despite being functionally equivalent for all correct inputs.
Portability
- This program requires
argvto point to writable memory. It doesn't require the actualargvstrings to be writable, though. - This program requires ASCII.
- This program doesn't work with
%estyle numbers like1e-4. - Some seemingly redundant code works to eliminate warnings and evade a gcc bug.
NOTICE to those who wish for a greater challenge:
If you want a greater challenge, don't read any further: just try to understand the program via the source.
If you get stuck, come back and read below for additional hints and information.
How this entry works:
The parser parses function names, subtraction, and division as single-letter unary operators. A bitmask encoded hash table is used to check no-ops/digits and another hash function maps the ASCII to a function ordinal, which is then executed by the button panel.
Both hash functions were found using a separate search program. Another program was used to find a way to format one hash function as example input such that it produces something resembling the bitmask hash table as part of its output.