Feat while statement

codegen/jasm.go

@@ -13,6 +13,8 @@ type JASM struct {
 	endIfLabel              string
 	elseLabel               string
 	repeatLabel             string
+	whileTestLabel          string
+	nextStatementLabel      string
 	st                      *SymbolTable
 }
 
@@ -111,6 +113,21 @@ func (j *JASM) FinishRepeatStatement() {
 	j.addOpcode("ifeq", j.repeatLabel)
 }
 
+func (j *JASM) StartWhileStatement() {
+	j.whileTestLabel = j.newLabel()
+	j.nextStatementLabel = j.newLabel()
+	j.addLabel(j.whileTestLabel)
+}
+
+func (j *JASM) FinishWhileStatement() {
+	j.addGotoOpcode(j.whileTestLabel)
+	j.addLabel(j.nextStatementLabel)
+}
+
+func (j *JASM) StartWhileBlock() {
+	j.addOpcode("ifeq", j.nextStatementLabel)
+}
+
 func (j *JASM) AddOperatorOpcode(op string) {
 	pt1 := j.pst.Pop()
 	pt2 := j.pst.Pop()

codegen/tree_shape_listener.go

@@ -125,6 +125,18 @@ func (t *TreeShapeListener) ExitRepeatStatement(ctx *parsing.RepeatStatementCont
 	t.jasm.FinishRepeatStatement()
 }
 
+func (t *TreeShapeListener) EnterWhileStatement(ctx *parsing.WhileStatementContext) {
+	t.jasm.StartWhileStatement()
+}
+
+func (t *TreeShapeListener) ExitWhileStatement(ctx *parsing.WhileStatementContext) {
+	t.jasm.FinishWhileStatement()
+}
+
+func (t *TreeShapeListener) EnterWhileBlock(ctx *parsing.WhileBlockContext) {
+	t.jasm.StartWhileBlock()
+}
+
 func (t *TreeShapeListener) Code() string {
 	return t.jasm.Code()
 }

parser/Pascal.g4

@@ -441,7 +441,11 @@ repetetiveStatement
     ;
 
 whileStatement
-    : WHILE expression DO statement
+    : WHILE expression whileBlock
+    ;
+
+whileBlock
+    : DO statement
     ;
 
 repeatStatement

tests/expected_jasm_files/while.jasm

@@ -0,0 +1,58 @@
+// Code generated by POJ 0.1
+public class while {
+	public static main([java/lang/String)V {
+		sipush 10
+		istore 1
+		L1:
+		iload 1
+		sipush 20
+		if_icmpge L3
+		iconst 1 
+		goto L4
+		L3:
+		iconst 0 
+		L4:
+		ifeq L2
+		getstatic java/lang/System.out java/io/PrintStream
+		ldc "i="
+		invokevirtual java/io/PrintStream.print(java/lang/String)V
+		getstatic java/lang/System.out java/io/PrintStream
+		iload 1
+		invokevirtual java/io/PrintStream.print(I)V
+		getstatic java/lang/System.out java/io/PrintStream
+		invokevirtual java/io/PrintStream.println()V
+		iload 1
+		sipush 1
+		iadd 
+		istore 1
+		goto L1
+		L2:
+		sipush 20
+		istore 1
+		L5:
+		iload 1
+		sipush 10
+		if_icmpgt L7
+		iconst 1 
+		goto L8
+		L7:
+		iconst 0 
+		L8:
+		ifeq L6
+		getstatic java/lang/System.out java/io/PrintStream
+		ldc "dont write i="
+		invokevirtual java/io/PrintStream.print(java/lang/String)V
+		getstatic java/lang/System.out java/io/PrintStream
+		iload 1
+		invokevirtual java/io/PrintStream.print(I)V
+		getstatic java/lang/System.out java/io/PrintStream
+		invokevirtual java/io/PrintStream.println()V
+		iload 1
+		sipush 1
+		iadd 
+		istore 1
+		goto L5
+		L6:
+		return
+	}
+}

tests/pascal_programs/while.pas

@@ -0,0 +1,19 @@
+program WhileExample;
+var
+  i: integer;
+begin
+  i := 10;
+  while i < 20 do
+  begin
+    writeln ('i=', i);
+    i := i + 1;
+  end;
+
+  i := 20;
+  while i <= 10 do
+  begin
+    writeln ('dont write i=', i);
+    i := i + 1;
+  end;
+
+end.