FunTang-Lambda Parser

gistfile1.txt

/* description: Parses end executes mathematical expressions. */

/* lexical grammar */
%lex
%%

\s+   { return 'SP'; }
"->"  { return 'AR'; }
"("   { return 'LP'; }
")"   { return 'RP'; }
","   { return 'TP'; }
"x"|"y" { return 'ID' }
<<EOF>> { return 'EOF'}

/lex

/* operator associations and precedence */

%left AR

%start exp

%% /* language grammar */

exp : fn EOF
      %{
          return $fn;
      %}
     ;

fn
    : arrow fn
      %{
           $$ = $arrow+$fn;
      %}
    | arrow apply
      %{
           $$ = $arrow+$apply ;
      %}
    ;

arrow
    : tuple AR
      %{
           $$ = $tuple+$AR;
      %}
    ;

apply 
    : ID SP apply
      %{
           $$ = "ENV["+$ID+"]"+$apply;
      %}
    | ID
      %{
           $$ = "ENV["+$ID+"]";
      %}
    ;

tuple
     : LP tlist RP
       %{
           $$ = $LP+$tlist+$RP
       %}
     ;

tlist
     : ID TP tlist
       %{
           $$ = $ID+","+$tlist
       %}
     | ID
       %{
           $$ = $ID
       %}
     | 
       %{
           $$ = ''
       %}
     ;