func TestEval(t *testing.T) {
addTree := ast.New()
addTree.AddChildren([]ast.Node{
&ast.Number{
Value: "2",
},
&ast.Operator{
Class: ast.OpAdd,
},
&ast.Number{
Value: "3",
},
})
subTree := ast.New()
subTree.AddChildren([]ast.Node{
&ast.Number{
Value: "5",
},
&ast.Operator{
Class: ast.OpSubtract,
},
&ast.Number{
Value: "3",
},
})
testCases := []struct {
tree ast.Node
expected *big.Rat
}{
{
tree: &ast.Number{
Value: "42",
},
expected: big.NewRat(42, 1),
},
{
tree: addTree,
expected: big.NewRat(5, 1),
},
{
tree: subTree,
expected: big.NewRat(2, 1),
},
}
for i, tc := range testCases {
tcInfo := fmt.Sprintf("test case: %d\ninput:\n%s\n", i, tc.tree.Format(0))
actual, err := Eval(tc.tree)
require.NoError(t, err)
assert.Exactly(t, tc.expected, actual, "\nexpected: %0.3f\ngot: %0.3f\n%s", ratFloat(tc.expected), ratFloat(actual), tcInfo)
}
}
func justNumber(value string) ast.Node {
base := ast.New()
base.AddChild(&ast.Number{
Value: value,
})
return base
}
// E'2 -> "(" E ")"
func ep2(buf *token.Buffer, tree ast.Node) (newTree ast.Node, err error) {
origPos := buf.Pos()
defer func() {
if err != nil {
buf.MustSeek(origPos)
}
}()
newTree = tree.Copy()
expr := ast.New()
newTree.AddChild(expr)
if err := termOpenParen(buf); err != nil {
return nil, err
}
if buf.Pos() >= buf.Len() {
return nil, io.EOF
}
eTree, err := e(buf, tree.Copy())
if err != nil {
return nil, err
}
expr.AddChildren(eTree.Children())
if buf.Pos() >= buf.Len() {
return nil, io.EOF
}
if err := termCloseParen(buf); err != nil {
return nil, err
}
return newTree, nil
}
func Parse(tokens []token.Token) (ast.Node, error) {
buf := token.NewBuffer(tokens)
root := ast.New()
tree, err := e(buf, root)
if err != nil {
if err == io.EOF {
return nil, errors.New("Unexpected end of input")
}
return nil, err
}
return tree, nil
}
func operation(a string, opClass ast.OpClass, b string) ast.Node {
base := ast.New()
base.AddChildren([]ast.Node{
&ast.Number{
Value: a,
},
&ast.Operator{
Class: opClass,
},
&ast.Number{
Value: b,
},
})
return base
}