controlflow

README

A package to remove goto statements from a Go syntax tree by rewriting them as conditionals and loops.

This is an ongoing project and is incomplete. Please experiment with it but don't rely on it.

Documentation and examples

controlflow documentation

References

• Taming Control Flow: A Structured Approach to Eliminating Goto Statements

Documentation

Index

• func ElimGotos(stmts []ast.Stmt) []ast.Stmt

Examples

• ElimGotos

Functions

func ElimGotos

func ElimGotos(stmts []ast.Stmt) []ast.Stmt

ElimGotos removes any goto statements from stmts by rewriting them as conditionals and loops. A transformed syntax tree is returned; stmts is not modified.

Example

code := `
package branchy
func isGoodNumber(x int) bool {

	if x%3 == 0 {
		goto fail
	} else if x%5 == 0 {
		goto fail
	}
    return true
fail:
	return false	
}
`

// Parse the code
fset := token.NewFileSet()
file, err := parser.ParseFile(fset, "code.go", code, 0)
if err != nil {
	panic(err)
}

// List of statements in the function's body
body := file.Decls[0].(*ast.FuncDecl).Body.List

// Rewrite the function body without goto statements
newBody := ElimGotos(body)

// Print the result
config := printer.Config{Mode: printer.UseSpaces, Tabwidth: 4}
config.Fprint(os.Stdout, token.NewFileSet(), newBody)

Output:

gotofail := false
if x%3 == 0 {
    gotofail = true
} else {
    gotofail = x%5 == 0
}
if !gotofail {
    return true
}
return false