如何使用Rascal从Java Eclipse项目中提取特定语句

Question

I am new to rascal and want to extract conditional statements (if,while,etc) from a java project.

The best method seems to be at http://tutor.rascal-mpl.org/Rascal/Libraries/analysis/m3/Core/containment/containment.html#/Rascal/Libraries/analysis/m3/AST/AST.html

My code so far is

    void statements(loc location) {
        ast = createAstFromFile(location,true,javaVersion="1.7");
        for(/Statement s := ast) println(readFile(s@src));
    }

But this returns all statements including comments. How do i filter the statements to only return conditional statements if,while,for,etc.?

Answer 1

Rascal implements the Visitor pattern for this. You could do something like this on your ast variable:

visit(ast){ 
    case \if(icond,ithen,ielse): {
        println(" if-then-else statement with condition <icond> found"); } 
    case \if(icond,ithen): {
        println(" if-then statement with condition <icond> found"); } 
};

This example returns the if statements from the code.

You can find the definitions of patterns to use as case patterns in the package lang::java::m3::AST .

Answer 2

@Geert-Jan Hut's answer is the best, because this is what visit is for.

Here is some other methods:

for(/\if(icond,ithen,ielse) s := ast) 
  println(readFile(s@src));

for(/\if(icond,ithen) s := ast) 
  println(readFile(s@src));

Or, because both constructors have the same name, you could use is :

for (/Statement s := ast, s is if)
  println(readFile(s@src));

Or, first collect them all and then print:

conds = { c | /Statement s := ast, s is if };
for (c <- conds) 
   println(readFile(c@src));