Bruno BELANYI
77a7bdfddd
This allows for having different tokens mapping to the same mathematical operator, with potentially different semantics. For example, we can add `$` as another notation for factorial, but allowing it to be chained: meaning we can evaluate `3$$` to `720`, and still keep `3!!` as a syntax error. To do so, we simply need to add the following line to our operator table: ```c POSTOP(UNOP_FACT, 5, ASSOC_LEFT, '$', 0) ``` |
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Evalexpr
This was a small experiment in writing a precedence climbing parser, using C. I also have my reference parsing implementation, using recursive descent, to compare the parsing results.
This is mostly based on the explanation found at this address: https://www.engr.mun.ca/~theo/Misc/exp_parsing.htm (use the Wayback Machine to read it).
How to build
Simply launch the following command
42sh$ make
If you want to build an evalexpr command using recursive descent instead, use:
42sh$ make USE_CLIMBING=0
Don't forget to use make clean when alternating between both.
How to use
Simply launch the binary, and write an expression on its standard input. The binary can parse exactly one expression per line, and reports parsing errors if they happen.
Example use:
42sh$ ./evalexpr
1 + 2 * 3 - 3!
1