# Strategies
## Interpretation
- **Portability** : no need to compile
- **Impact on the input language** : first order eval function, dynamic everything

## Virtual machines
Allows processor emulation to allow execution on any platform

## Transpilation
Conversion from a language to another (e.g. Arduino $\rightarrow$ C)
## Compilation
**Ahead of time** compilation : produce a binary file that can be run in the targeted architecture
**Just in time** compilation : involves compilation during execution

## Bytecode strategy
- portable
- low level
- no physical machine can understand it
- can be :
	- compiled
	- interpreted
	- executed by a VM

# Development tools

- Use warnings
- Use **assert/static_assert** (C++11)
- {Address,Thread,Memory,Leaks}Sanitizer
- lcov
## Autotools

- **autoconf** : package configuration
- **automake** : package build
- **libtool** : a portable build of shared libs
- **gettext** : 

# Lexical analysis

$$
chars \rightrightarrows SCAN \rightrightarrows tokens
$$

## Flex

- **F**ast **L**exical Analyzer generator
- GNU version of Lex
- TC now uses RE/Flex
### Variables
- **yytext** : token text
- **yyleng** : size of token text
- **yylex** : starts the scanning
- **yywrap** : called when end of text is encountered, can be redefined if needed

## Bison

- **yyparse**
- **yyerror**

## Coupling Flex & Bison

```sh
$ bison -o parser.cc -d --graph tmp.yy
$ flex -o lexer.cc tmp.ll
$ g++ -std=c++20 lexer.cc parser.cc
$ echo "1+2+3+98" | ./a.out
104
$ echo "1+2+3++98" | ./a.out
1.7: syntax error, unexpected +, expecting number
0
```
## Error recovery