Merge pull request #39 from frungl/master

`rangeto`, `downto` keywords for the for block

README.md

@@ -214,6 +214,10 @@ It first assigns the value of expression `<start>` to variable `<name>`.
 Then, as long as `<name>` is strictly less than the value of expression `<finish>`,
 the statements are executed from top to bottom, the variable is increased by one,
 and the condition is evaluated again.
+You can also write `rangeto`/`downto` instead of `until`.
+Then, as long as `<name>` is not strictly less/more respectively, the value of the expression `<finish>`,
+the statements are executed from top to bottom, the variable is increased/decreased, respectively, by one,
+and the condition is evaluated again.
 
 ### Expressions
 

README.ru.md

@@ -241,7 +241,11 @@ function <name> (<arg1>, <arg2>, ...):
 переменной с именем `<name>`.
 Затем, пока `<name>` строго меньше значения выражения `<finish>`,
 команды выполняются сверху вниз, значение переменной увеличивается на единицу,
-после чего условие проверяется снова.
+после чего условие проверяется снова. 
+Также вы можете написать `rangeto`/`downto` вместо `until`.
+Затем, пока `<name>` нестрого меньше/больше соответственно, значения выражения `<finish>`,
+команды выполняются сверху вниз, значение переменной увеличивается/уменьшается соответственно, на единицу,
+после чего условие проверяется снова. 
 
 ### Выражения
 

examples/for.pr

@@ -0,0 +1,10 @@
+function for(id, pr, n, a):
+	if id == 0:
+		left := 1
+		right := 3
+		for i := left until right:
+			print(i)
+		for i := left rangeto right:
+			print(i)
+		for i := right downto left:
+			print(i)

extra/Notepad++-syntax-highlighting/pr.xml

@@ -25,7 +25,7 @@
             <Keywords name="Folders in comment, middle"></Keywords>
             <Keywords name="Folders in comment, close"></Keywords>
             <Keywords name="Keywords1">function array</Keywords>
-            <Keywords name="Keywords2">for until while if elif else</Keywords>
+            <Keywords name="Keywords2">for until rangeto downto while if elif else</Keywords>
             <Keywords name="Keywords3">send receive print</Keywords>
             <Keywords name="Keywords4">id</Keywords>
             <Keywords name="Keywords5">pr</Keywords>

source/display.d

@@ -117,7 +117,7 @@ void display (Statement s, int indent)
 		{
 			write ("for ", cur.name, " := ");
 			display (cur.start);
-			write (" until ");
+			writef (" %s ", forStyleNames[cur.style]);
 			display (cur.finish);
 			writeln (":");
 			foreach (r; cur.statementList)

source/language.d

@@ -67,17 +67,28 @@ final class WhileBlock : Statement
 	}
 }
 
+final enum ForStyle
+{
+	until, 
+	rangeto, 
+	downto
+}
+
+immutable string[] forStyleNames = ["until", "rangeto", "downto"];
+
 final class ForBlock : Statement
 {
 	string name;
+	ForStyle style;
 	Expression start;
 	Expression finish;
 	Statement [] statementList;
 
-	this (int lineId_, string name_, Expression start_, Expression finish_)
+	this (int lineId_, string name_, ForStyle style_, Expression start_, Expression finish_)
 	{
 		lineId = lineId_;
 		name = name_;
+		style = style_;
 		start = start_;
 		finish = finish_;
 		complexity = 1 + 1 + start.complexity + finish.complexity;

source/parser.d

@@ -411,13 +411,24 @@ final class StatementParser
 		    (line, "bad name: " ~ line.tokens.front);
 		line.tokens.consume (":=", line);
 		auto start = parseExpression (line);
-		line.tokens.consume ("until", line);
+		ForStyle style;
+		auto count = forStyleNames.countUntil (line.tokens.front);
+		if (count < 0) 
+		{
+			check (false, line, '\'' ~ line.tokens.front ~ "\' is not the keyword of the for block");
+		}
+		else 
+		{
+			style = cast (ForStyle) count;
+			line.tokens.consume (forStyleNames[count], line);
+		}
+
 		auto finish = parseExpression (line);
 		line.tokens.consume (":", line);
 		check (line.tokens.empty, line,
 		    "extra token at end of line: " ~ line.tokens.front);
 
-		ForBlock res = new ForBlock (line.lineId, name, start, finish);
+		ForBlock res = new ForBlock (line.lineId, name, style, start, finish);
 		res.statementList = parseBlock (prevIndent);
 		return res;
 	}

source/runner.d

@@ -531,6 +531,29 @@ class Runner
 				return true;
 			}
 
+			bool hasNext (long value, long finishValue, ForStyle style) {
+				final switch (style) {
+					case ForStyle.until:
+						return value < finishValue;
+					case ForStyle.rangeto:
+						return value <= finishValue;
+					case ForStyle.downto:
+						return value >= finishValue;
+				}
+			}
+
+			void setValueNext (ref long value, ForStyle style) {
+				final switch (style) {
+					case ForStyle.rangeto:
+					case ForStyle.until:
+						value += 1;
+						break;
+					case ForStyle.downto:
+						value -= 1;
+						break;
+				}
+			}
+
 			auto cur3 = cast (ForBlock) (parent);
 			if (cur3 !is null) with (cur3)
 			{
@@ -544,7 +567,7 @@ class Runner
 					vars[name] = Var (startValue);
 					delay = complexity;
 					delay += 3;
-					if (vars[name].value < finishValue)
+					if (hasNext (vars[name].value, finishValue, style))
 					{
 						pos += 1;
 					}
@@ -557,9 +580,9 @@ class Runner
 				{
 					auto finishValue =
 					    evalExpression (finish);
-					vars[name].value += 1;
+					setValueNext (vars[name].value, style);
 					delay += 7;
-					if (vars[name].value < finishValue)
+					if (hasNext (vars[name].value, finishValue, style))
 					{
 						pos = 0;
 					}

syntax.txt

@@ -109,6 +109,8 @@ while <expression0> : \n <statement-list>
 
 <for-block> is
 for <name> := <expression0> until <expression0> : \n <statement-list>
+for <name> := <expression0> rangeto <expression0> : \n <statement-list>
+for <name> := <expression0> downto <expression0> : \n <statement-list>
 
 <if-block> is
 if <expression0> : \n <statement-list>