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# IMP Interpreter
A small interpreter of the IMP programming language.
## Build
- `make all` to build interpreter.
- `make repl` to run repl.
- `make example` to interpret "example/example.imp".
- `make clean` to remove build folder.
## Dependencies
- [flex](https://github.com/westes/flex)
- [bison](https://www.gnu.org/software/bison)
- [readline](https://tiswww.case.edu/php/chet/readline/rltop.html)
## IMP
[Syntax](/res/syntax.ebnf)
**Statement `<stm>`**
Variable assignment:
- `<var> := <aexp>` any variable not assigned, has the value 0.
Local variable:
- `var <var> := <aexp> in <stm> end`
Control flow:
- `if <bexp> then <stm> else <stm> end`
- `while <bexp> do <stm> end`
- `(<stm>; <stm>)` sequential composition, the first statement runs before the second
- `skip`, nop
**Expression**
Arithmetic Expression `<aexp>`:
- `<num>`
- `<var>`
- `(<aexp> + <aexp>)`
- `(<aexp> - <aexp>)`
- `(<aexp> + <aexp>)`
Boolean Expression `<bexp>`:
- `not <bexp>`
- `(<bexp> or <bexp>)`
- `(<bexp> and <bexp>)`
- `<aexp> = <aexp>`
- `<aexp> # <aexp>` not equals
- `<aexp> < <aexp>`
- `<aexp> <= <aexp>`
- `<aexp> > <aexp>`
- `<aexp> >= <aexp>`
**Variable `<var>`**
- `[a-zA-Z][A-Za-z0-9]*`
**Numeral `<num>`**
- `[0-9]+`
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