Merge pull request #1537 from openscad/lc-extensions-cstyle-for

Extend List-Comprehension with c-style for

src/expr.cc

@@ -657,6 +657,47 @@ void ExpressionLcFor::print(std::ostream &stream) const
     stream << "for(" << this->call_arguments << ") (" << *this->first << ")";
 }
 
+ExpressionLcForC::ExpressionLcForC(const AssignmentList &arglist, const AssignmentList &incrargs, Expression *cond, Expression *expr)
+    : ExpressionLc(cond, expr), call_arguments(arglist), incr_arguments(incrargs)
+{
+}
+
+ValuePtr ExpressionLcForC::evaluate(const Context *context) const
+{
+	ExperimentalFeatureException::check(Feature::ExperimentalForCExpression);
+
+	Value::VectorType vec;
+
+    Context c(context);
+    evaluate_sequential_assignment(this->call_arguments, &c);
+
+	unsigned int counter = 0;
+    while (this->first->evaluate(&c)) {
+        vec.push_back(this->second->evaluate(&c));
+
+		if (counter++ == 1000000) throw RecursionException::create("for loop", "");
+
+        Context tmp(&c);
+        evaluate_sequential_assignment(this->incr_arguments, &tmp);
+        c.apply_variables(tmp);
+    }    
+
+    if (this->second->isListComprehension()) {
+        return ValuePtr(flatten(vec));
+    } else {
+        return ValuePtr(vec);
+    }
+}
+
+void ExpressionLcForC::print(std::ostream &stream) const
+{
+    stream
+        << "for(" << this->call_arguments
+        << ";" << *this->first
+        << ";" << this->incr_arguments
+        << ") " << *this->second;
+}
+
 ExpressionLcLet::ExpressionLcLet(const AssignmentList &arglist, Expression *expr)
     : ExpressionLc(expr), call_arguments(arglist)
 {

src/expression.h

@@ -259,6 +259,17 @@ private:
 	AssignmentList call_arguments;
 };
 
+class ExpressionLcForC : public ExpressionLc
+{
+public:
+	ExpressionLcForC(const AssignmentList &arglist, const AssignmentList &incrargs, Expression *cond, Expression *expr);
+	ValuePtr evaluate(const class Context *context) const;
+	virtual void print(std::ostream &stream) const;
+private:
+	AssignmentList call_arguments;
+	AssignmentList incr_arguments;
+};
+
 class ExpressionLcEach : public ExpressionLc
 {
 public:

src/feature.cc

@@ -21,6 +21,7 @@ Feature::list_t Feature::feature_list;
  */
 const Feature Feature::ExperimentalEachExpression("lc-each", "Enable <code>each</code> expression in list comprehensions.");
 const Feature Feature::ExperimentalElseExpression("lc-else", "Enable <code>else</code> expression in list comprehensions.");
+const Feature Feature::ExperimentalForCExpression("lc-for-c", "Enable C-style <code>for</code> expression in list comprehensions.");
 
 Feature::Feature(const std::string &name, const std::string &description)
 	: enabled(false), name(name), description(description)

src/feature.h

@@ -16,6 +16,7 @@ public:
 
         static const Feature ExperimentalEachExpression;
         static const Feature ExperimentalElseExpression;
+        static const Feature ExperimentalForCExpression;
 
 	const std::string& get_name() const;
 	const std::string& get_description() const;

src/parser.y

@@ -467,6 +467,12 @@ list_comprehension_elements:
                 }
                 delete $3;
             }
+        | TOK_FOR '(' arguments_call ';' expr ';' arguments_call ')' list_comprehension_elements_or_expr
+            {
+                $$ = new ExpressionLcForC(*$3, *$7, $5, $9);
+                delete $3;
+                delete $7;
+            }
         | TOK_IF '(' expr ')' list_comprehension_elements_or_expr
             {
               $$ = new ExpressionLcIf($3, $5, 0);

testdata/scad/functions/list-comprehensions-experimental.scad

@@ -6,3 +6,5 @@ echo([ for (a = [0 : 3]) if (a < 2) ( if (a < 1) ["+", a] ) else ["-", a] ]);
 echo([ for (a = [2 : 4]) each [ a, a*a ] ]);
 function f() = [ for (a = [0 : 4]) pow(2, a) ];
 echo([ each ["a", "b"], each [-5 : -2 : -9], each f(), each "c", each 42, each true ]);
+echo([ for (i=2;i<=10;i=i+2) i ]);
+echo([ for (i=1,n=1;i<=4;i=i+1,n=(n+i)*i) [i,n] ]);

testdata/scad/misc/allexpressions.scad

@@ -34,3 +34,4 @@ ee = ["abc", for (a=[0,1]) let(b=a) if (true) b, true, for(c=[1:3]) c, 3];
 ff = [for (a=[0,1]) if (a == 0) "A" else ( "B" )];
 gg = [each [ "a", 0, false ]];
 hh = [for (a = [0 : 3]) if (a < 2) ( if (a < 1) ["+", a] ) else ["-", a] ];
+ii = [for (a=0,b=1;a < 5;a=a+1,b=b+2) [a,b*b] ];

tests/CMakeLists.txt

@@ -997,7 +997,7 @@ function(add_cmdline_test TESTCMD_BASENAME)
       if (${EXPERIMENTAL} EQUAL -1)
         set(EXPERIMENTAL_OPTION "")
       else()
-        set(EXPERIMENTAL_OPTION "--enable=lc-each" "--enable=lc-else")
+        set(EXPERIMENTAL_OPTION "--enable=lc-each" "--enable=lc-else" "--enable=lc-for-c")
       endif()
 
       # 2D tests should be viewed from the top, not an angle.

tests/regression/echotest/list-comprehensions-experimental-expected.echo

@@ -5,3 +5,5 @@ ECHO: [["+", 0], ["-", 1]]
 ECHO: [["+", 0], ["-", 2], ["-", 3]]
 ECHO: [2, 4, 3, 9, 4, 16]
 ECHO: ["a", "b", -5, -7, -9, 1, 2, 4, 8, 16, "c", 42, true]
+ECHO: [2, 4, 6, 8, 10]
+ECHO: [[1, 1], [2, 6], [3, 27], [4, 124]]

tests/regression/moduledumptest/allexpressions-expected.ast

@@ -34,4 +34,4 @@ ee = ["abc", for(a = [0, 1]) (let(b = a) (if(true) (b))), true, for(c = [1 : 3])
 ff = [for(a = [0, 1]) (if((a == 0)) ("A") else ("B"))];
 gg = [each (["a", 0, false])];
 hh = [for(a = [0 : 3]) (if((a < 2)) (if((a < 1)) (["+", a])) else (["-", a]))];
-
+ii = [for(a = 0, b = 1;(a < 5);a = (a + 1), b = (b + 2)) [a, (b * b)]];