[Ongoing] Rewrite frontend to use Flex/Bison

This is a merge of another experiment, so the changes are large:

- separated "modules" directory into frontend/backend
  - adjusted module names and moved files for this to happen
- removed modules lexer & parser
- removed all the unit tests (most were outdated)
- added Bison, flex, and C development tools to manifest.scm
- added lexer.l, a source file used by the flex utility with a functioning lexing implementation
- added parser.y, a source file used by the bison utility with a functioning parser implementation
- added node.c and node.h, which parser.y uses to construct an AST of a C source file (up to binary ops)
- added driver.c, a Guile-C interface that provides a module to scheme programs
- added a Makefile to make all of this
- added stuff to .gitignore

1 files changed, 47 insertions, 0 deletions

diff --git a/src/frontend/lexer.l b/src/frontend/lexer.l
new file mode 100644
index 0000000..5b72086
--- /dev/null
+++ b/src/frontend/lexer.l
@@ -0,0 +1,47 @@
+/*** definition section ***/
+%{
+  /* C to be copied verbatim */
+  #include "parser.h"
+%}
+
+/* read only one input file */
+%option noyywrap
+%option yylineno
+
+DIGIT    [0-9]
+ALPHA    [[:alpha:]_]
+
+/*** rules section ***/
+%%
+
+"("             {return L_PAREN;}
+")"             {return R_PAREN;}
+"{"             {return L_BRACK;}
+"}"             {return R_BRACK;}
+";"             {return SEMI_COL;}
+"~"             {return COMP;}
+"*"             {return MULT;}
+"/"             {return DIV;}
+"%"             {return MOD;}
+"-"             {return MINUS;}
+"+"             {return PLUS;}
+
+"int"           {return INT;}
+"void"          {return VOID;}
+"return"        {return RET;}
+
+{DIGIT}+        {yylval.ival = atol(yytext); return NUMBER;}
+{ALPHA}+        {
+  yylval.sval = strdup(yytext);
+  return WORD;
+       }
+
+[[:space:]]+    {/* discard */}
+.               {
+  printf("Error at line %d: unrecognized symbol \"%s\"\n", yylineno, yytext);
+  return YYerror;
+}
+
+%%
+
+/*** C section ***/