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# Frontend for language
Tiny beginnings of a parser for a toy language, written in C99.
Currently only capable of parsing simple arithmetic expressions, limited to
positive numbers, addition, subtraction, multiplication, and division.
## Compiling
To build `frontend`:
```
make
```
## Running
Simply run `./frontend INPUT_FILE` and it should parse and print the resulting
AST in polish notation with surrounding parenthesis,
ie. `1 + 2 * 3` turns into `( + 1 ( * 2 3 ) )`,
and `1 + 2 + 3` becomes `( + ( + 1 2 ) 3 )`.
Example input can be found in the `program.input` file.
## Next steps
* Allocating all memory up front, an inefficient but very simple use of memory
would exploit the fact that the number of lines and tokens is bounded by the total
number of bytes in `INPUT_FILE`, and the number of sub-expressions are bounded
by the number of tokens, so a naive approach is to allocate
`length(INPUT_FILE) * sizeof(char + line_t + expression_t)`.
* Streaming parsing; the implementation currently supports reading a limited
amount of input at each step, extending it to "pause-at-X" and resume once
more input is available should be a trivial feat.
* Fix precedence implementation, currently we just compare operators, which is
unmaintainable and inefficient once the grammar is extended.
* Extend the arithmetic grammar to support more operators.
* Boolean grammar parsing.
* Argument parsing to better control the output and debug different parts of the
implementation.
* Tests.
Currently only simple arithmetic is implemented.
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