/
minus_plus.go
103 lines (77 loc) · 1.79 KB
/
minus_plus.go
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package arithmetic
// minus (-) operator.
type minus struct{}
func (o minus) String() string {
return "-"
}
func (o minus) precedence() uint8 {
return precedenceMinusPlus
}
func (o minus) solve(st *stack) (interface{}, error) {
// Retreive right and left terms from stack.
// The terms can be of type "float" or "variable".
o2, err := st.popFloat()
if err != nil {
return nil, rightError(o)
}
o1, err := st.popFloat()
if err != nil {
return nil, leftError(o, o2)
}
return o1 - o2, nil
}
// unary minus (-) operator.
type unaryMinus struct{}
func (o unaryMinus) String() string {
return "-"
}
func (o unaryMinus) precedence() uint8 {
return precedenceUnary
}
func (o unaryMinus) solve(st *stack) (interface{}, error) {
// Retreive right term from stack.
// The term can be of type "float" or "variable".
right, err := st.popFloat()
if err != nil {
return nil, rightError(o)
}
return -right, nil
}
// plus (+) operator.
type plus struct{}
func (o plus) String() string {
return "+"
}
func (o plus) precedence() uint8 {
return precedenceMinusPlus
}
func (o plus) solve(st *stack) (interface{}, error) {
// Retreive right and left terms from stack.
// The terms can be of type "float" or "variable".
o2, err := st.popFloat()
if err != nil {
return nil, rightError(o)
}
o1, err := st.popFloat()
if err != nil {
return nil, leftError(o, o2)
}
return o1 + o2, nil
}
type unaryPlus struct{}
func (o unaryPlus) String() string {
return "+"
}
// unary plus (-) operator.
func (o unaryPlus) precedence() uint8 {
return precedenceUnary
}
func (o unaryPlus) solve(st *stack) (interface{}, error) {
// Retreive right term from stack.
// The term can be of type "float" or "variable".
right, err := st.popFloat()
if err != nil {
return nil, rightError(o)
}
return right, nil
}