Init commit

Makefile

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+.PHONY: all clean
+all: deelang
+
+lexer.o lexer.h: parser.h lexer.l
+	flex -o lexer.c --header-file=lexer.h lexer.l
+	$(CC) -c lexer.c
+	rm lexer.c
+
+parser.h parser.o: parser.y
+	bison -o parser.c --header=parser.h parser.y
+	$(CC) -c parser.c
+	rm parser.c
+
+deelang: deelang.c lexer.o parser.o
+	$(CC) -o $@ $^
+
+clean:
+	rm -rf parser.o lexer.o parser.h lexer.h deelang

blockexample.dee

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+fun <- ->
+    do-something()
+    do-something-else()
+
+
+foo <- ->
+    bar <- ->
+        baz <- ->
+            print("Deep in here")
+    print ("Inside foo but not in baz or bar")
+
+foo() ## Inside foo but not in baz or bar
+
+add <- x -> y ->
+    return x + y

deelang.c

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+#include "lexer.h"
+#include "parser.h"
+
+void main() {
+  yydebug = 1;
+  yyparse();
+}

example.dee

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+## By the end of the book I want to have an interpreter
+## for this little language, maybe a compiler too
+
+print(1 + 1) ## 2
+print("Hello world!") ## Hello world
+
+name <- read()
+print("Hi there $name") ## Hi there <name>
+
+have <- 10
+want <- 11
+need <- have - want ## This is subtraction
+have-want <- 1 ## This is a variable named "have-want"
+
+print HaVe-WAnt ## 1 (case doesn't matter)
+%%option meaningful-casing
+Apples <- 1
+print apples ## <undef> (or maybe it does)
+
+print("one fish"); print("two fish") ## Two variables on the same line
+
+say-hi <- -> print("Hi from inside a function")
+say-hi() ## Hi from inside a function
+
+say-hi-again <- say-hi
+say-hi-again() ## "Hi from inside a function" (First class functions!)
+
+duck <- {
+	bills <- 1
+	talk <- -> print("Quack")
+	eats? <- food -> food = "bread"
+} ## Objects created on the fly
+
+print duck.eats?("bread") ## true
+print duck.eats?("corn") ## false
+
+cow <- {
+	talk <- print("Moo")
+	eats? <- food -> food oneof "grass", "corn"
+}
+
+human <- {
+	eats? <- _ -> true
+}
+
+print cow.eats?("grass") ## true
+print cow.eats?("corn") ## true
+
+talk-or-pass-wind <- character ->
+	if character has talk then
+		character.talk()
+	else
+		print("*Fart*")
+
+talk-or-pass-wind(duck) ## "Quack"
+talk-or-pass-wind(cow) ## "Moo"
+talk-or-pass-wind(human) ## "*Fart*"

lexdemo.c

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+#include "lexer.h"
+#include "parser.h"
+
+void main() {
+  int t;
+  while ((t = yylex()) != 0) {
+    printf("yylex=0x%x\n", t);
+    printf("yylval=%s\n", yylval.sym);
+  }
+  printf("Byebye!");
+}

lexer.l

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+%{
+#include "parser.h"
+int stack[100]; // Max indentation depth
+int sp = -1;
+int peek();
+void push(int a);
+void pop();
+#define YY_USER_INIT push(0); BEGIN(freshline);
+%}
+
+%option noyywrap
+
+%x freshline
+
+digit	[0-9]
+letter	[A-Za-z]
+
+%%
+<freshline>""/[^\t ]		{
+if (peek() == 0) {
+   BEGIN(0);
+} else {
+  pop(); yyless(0); return DEDENT;
+}
+				}
+<freshline>[ \t]+		{
+if (peek() == yyleng) {
+  BEGIN(0); // Same indentation, continue
+} else if (peek() > yyleng) {
+  pop(); yyless(0); return DEDENT;
+  // Same rule again until the stack is even
+} else {
+  push(yyleng); BEGIN(0); return INDENT;
+}
+	       			}
+#[^\n]*					// Eat comments
+\"[^"]*\"				yylval.sym = yytext; return STRING;
+if					return IF;
+else					return ELSE;
+elif 					return ELIF;
+{digit}+|{digit}*\.{digit}+		yylval.num = atof(yytext); return NUM;
+{letter}({letter}|{digit}|[?-])*	yylval.sym = yytext; return ID;
+"<-"					return GETS;
+"->"					return MAPS;
+[().,*/+-]				return yytext[0];
+[\t ]					// Eat whitespace not first on a line
+"/"\n					// Eat newlines ending in /
+[\n;]					BEGIN(freshline); return STOP;
+.					fprintf(stderr, "Scanning error!\nOffender: %s\n", yytext); exit(1);
+%%
+
+int peek() {
+    printf("Peek @ %d\n", stack[sp]);
+    return stack[sp];
+}
+
+void push(int a) {
+     printf("Push @ %d\n", a);
+     sp++;
+     stack[sp] = a;
+}
+
+void pop() {
+     printf("Pop! Sp @ %d\n", sp);
+     sp--;
+}

parser.y

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+%{
+#include <stdio.h>
+int yylex();
+int yyerror(const char* p) { fprintf(stderr, p); }
+%}
+
+%define parse.trace
+
+%union {
+       char* sym;
+       float num;
+}
+
+%token <sym> ID
+%token STOP
+%token <num> NUM
+%token STRING
+%token INDENT DEDENT
+%token IF ELIF ELSE
+
+%right GETS
+%left '+' '-'
+%left '/' '*'
+%left MAPS
+
+%%
+program:	statements | statements statement;
+statements:	statements statement STOP
+		| statements STOP
+		| // null production ;
+statement: 	assignment | funcall | conditional;
+assignment: 	ID GETS expr;
+expr:		funcdef
+		| funcall
+		| expr '+' expr
+		| expr '-' expr
+		| expr '*' expr
+		| expr '/' expr
+		| '(' expr ')'
+		| ID | NUM | STRING;
+		
+funcdef: 	param MAPS expr | param MAPS block;
+param:	 	ID | '_' | // null production;
+funcall: 	ID '(' exprlist ')'
+exprlist:	exprlist ',' expr | expr | // null production;
+
+conditional: 	IF expr block elifs
+		| IF expr block elifs ELSE block;
+elifs:		ELIF expr block elifs| // null production;
+
+block: 		STOP INDENT statement statements DEDENT
+%%