Blocks as statements.

README.md

@@ -19,9 +19,10 @@ Increments:
 - [X] Branching (if statements)
 - [X] While Loops
 - [X] Comparisons
-- [ ] Blocks as statements
-- [ ] Strings (WriteLn("Hello World"))
+- [X] Blocks as statements
 - [ ] For Loops
+- [ ] Strings (WriteLn("Hello World"))
+- [ ] Type Checking
 - [ ] Procedures
 - [ ] Functions
 - [ ] Arrays

src/HSPC/CodeGen.hs

@@ -88,6 +88,8 @@ generateStatement offsetMap (Halt ast) =
     -- exit_group syscall, exit code is in rdi
     ++ [0xb8, 0x3c, 00, 00, 00] -- mov rax 60
     ++ [0x0f, 0x05] -- Syscall
+generateStatement offsetMap (StatementBlock body) =
+  concatMap (generateStatement offsetMap) body
 generateStatement offsetMap (Assignment name op) =
   generateExpression offsetMap op
     ++ case Map.lookup name offsetMap of
@@ -114,6 +116,12 @@ generateExpression offsetMap (Identifier str) =
   case Map.lookup str offsetMap of
     Just offset -> [0x48, 0x8b, 0x85] ++ int32ToLE offset -- mov rax [rbp - n]
     Nothing -> error $ "Variable " ++ str ++ " doesn't exist."
+generateExpression offsetMap (Subtract op1 op2) =
+  generateExpression offsetMap op2
+    ++ [0x50] -- push rax
+    ++ generateExpression offsetMap op1
+    ++ [0x48, 0x2b, 0x04, 0x24] -- sub rax, [rsp]
+    ++ [0x48, 0x83, 0xc4, 0x08] -- add rsp, 8 (release stack space)
 generateExpression offsetMap (Add op1 op2) =
   generateExpression offsetMap op1
     ++ [0x50] -- push rax
@@ -158,4 +166,3 @@ generateExpression offsetMap (BoolAnd op1 op2) =
 generateExpression offsetMap (BoolNot op) =
   generateExpression offsetMap op
     ++ [0x48, 0x83, 0xf0, 0x01] -- xor rax, 0x1
-generateExpression _ ast = error $ "CodeGen for " ++ show ast ++ " not implemented"

src/HSPC/Parse.hs

@@ -32,6 +32,7 @@ data Statement
   | NOP
   | Assignment String Expression
   | Halt Expression
+  | StatementBlock [Statement]
   | ExprStmt Expression
   deriving (Show, Eq)
 
@@ -88,10 +89,10 @@ parse _ = Left MustStartWithProgramStatement
 parseMainProgramBlock :: [HSPCToken] -> Either ParseError Block
 parseMainProgramBlock (VarKeyWordTok : tocs) = do
   (vars, rest) <- parseVariableDeclarations [] tocs
-  (res, _) <- parseStatements [] rest
+  (res, _) <- parseStatements ProgramEndKeyWordTok [] rest
   return $ MainProgramBlock vars res
 parseMainProgramBlock (BeginKeyWordTok : tocs) = do
-  (res, _) <- parseStatements [] tocs
+  (res, _) <- parseStatements ProgramEndKeyWordTok [] tocs
   return $ MainProgramBlock [] res
 parseMainProgramBlock _ = Left InvalidStartOfBlock
 
@@ -126,13 +127,14 @@ splitToMatchingBracket toks = go toks [] 0
     go (x : xs) acc i = go xs (x : acc) i
     go [] _ _ = Left UnmatchedBracket
 
-parseStatements :: [Statement] -> [HSPCToken] -> Either ParseError ([Statement], [HSPCToken])
-parseStatements acc (EndKeyWordTok : xs) = Right (reverse acc, xs)
-parseStatements _ [] = Left ExpectedEndStatement
-parseStatements acc xs = do
+parseStatements :: HSPCToken -> [Statement] -> [HSPCToken] -> Either ParseError ([Statement], [HSPCToken])
+parseStatements endTok acc (x : xs)
+  | x == endTok = Right (reverse acc, xs)
+parseStatements _ _ [] = Left ExpectedEndStatement
+parseStatements endTok acc xs = do
   (expr, restWithSemiColon) <- parseStatement xs
   rest <- removeLeadingSemiColon restWithSemiColon
-  parseStatements (expr : acc) rest
+  parseStatements endTok (expr : acc) rest
 
 parseStatement :: [HSPCToken] -> Either ParseError (Statement, [HSPCToken])
 parseStatement (IdentifierTok name : AssignmentTok : xs) = do
@@ -146,6 +148,9 @@ parseStatement
     (internal, rest) <- splitToMatchingBracket xs
     op <- parseExpression internal
     return (Halt op, rest)
+parseStatement (BeginKeyWordTok : xs) = do
+  (stmts, rest) <- parseStatements EndKeyWordTok [] xs
+  return (StatementBlock stmts, rest)
 
 -- "IF cond THEN statement (; | ELSE elseStatement;)"
 -- ELSE IF is simply an if statement where elseSatement

src/HSPC/Tokenize.hs

@@ -13,6 +13,7 @@ data HSPCToken
   | VarKeyWordTok
   | BeginKeyWordTok
   | EndKeyWordTok
+  | ProgramEndKeyWordTok
   | WhileKeyWordTok
   | DoKeyWordTok
   | IfKeyWordTok
@@ -54,7 +55,7 @@ tokenize ('{' : cs) = tokenize $ dropWhile (/= '}') cs
 tokenize (c : cs)
   | "//" `isPrefixOf` (c : cs) = tokenize $ dropWhile (/= '\n') cs
   -- End includes this annoying '.'
-  | "END." `isPrefixOf` map toUpper (c : cs) = EndKeyWordTok : tokenize (drop 3 cs)
+  | "END." `isPrefixOf` map toUpper (c : cs) = ProgramEndKeyWordTok : tokenize (drop 3 cs)
   | isSpace c = tokenize cs
   | isDigit c =
       let (num, rest) = span isDigit (c : cs)
@@ -73,6 +74,7 @@ tokenizeIdentifierOrKeyWord "IF" = IfKeyWordTok
 tokenizeIdentifierOrKeyWord "ELSE" = ElseKeyWordTok
 tokenizeIdentifierOrKeyWord "THEN" = ThenKeyWordTok
 tokenizeIdentifierOrKeyWord "BEGIN" = BeginKeyWordTok
+tokenizeIdentifierOrKeyWord "END" = EndKeyWordTok
 tokenizeIdentifierOrKeyWord "HALT" = HaltBuiltInTok
 tokenizeIdentifierOrKeyWord "DIV" = IntDivideTok
 tokenizeIdentifierOrKeyWord "INTEGER" = IntegerTypeTok

test/Main.hs

@@ -28,6 +28,7 @@ testSuite =
     TestSpec "Exit code > 255" "ints_big_exit_code" 255,
     TestSpec "Halt after Halt" "ints_halt_after_halt" 0,
     TestSpec "Add literal ints" "operators_add_two_ints" 200,
+    TestSpec "Subtract literal ints" "operators_sub_two_ints" 90,
     TestSpec "Multiply literal ints" "operators_multiply_two_ints" 40,
     TestSpec "Divide(div) literal ints" "operators_divide_two_ints" 2,
     TestSpec "Brackets with literal ints" "operators_brackets" 26,
@@ -44,9 +45,11 @@ testSuite =
     TestSpec "IF ELSE" "if_else" 40,
     TestSpec "IF ELSE IF" "if_else_if" 40,
     TestSpec "IF with complex cond" "if_complex_cond" 40,
+    TestSpec "IF with block" "if_block" 15,
     TestSpec "WHILE basic example" "while" 0,
     TestSpec "WHILE not equal (<> 10)" "while_not_equal_10" 10,
     TestSpec "WHILE less than (< 1000)" "while_less_than" 100,
+    TestSpec "WHILE with block" "while_block" 250,
     TestSpec "Greater than (> and >=)" "comparison_greater_than" 40,
     TestSpec "Less than (< and <=)" "comparison_less_than" 23,
     TestSpec "Equality (= and <>)" "comparison_equality" 22

test/sample_programs/if_block.pas

@@ -0,0 +1,16 @@
+program IfExample;
+
+var 
+    i : integer;
+begin
+    i := 10;
+
+    if (True) then
+        begin
+            i := 10;
+            i := 20;
+            i := 15;
+       end;
+
+    halt(i); 
+end.

test/sample_programs/operators_sub_two_ints.pas

@@ -0,0 +1,5 @@
+program SubtractExample;
+
+begin
+    halt(100-10); 
+end.

test/sample_programs/while_block.pas

@@ -0,0 +1,18 @@
+program WhileExample;
+
+var 
+    i : integer;
+    j : integer;
+begin
+    i := 0;
+    j := 0;
+
+    while i < 25 do
+        begin
+         j := (j + 20) - 10;
+         i := i + 1;
+        end;
+
+
+    halt(j); 
+end.