/
lower_greater.go
144 lines (111 loc) · 2.38 KB
/
lower_greater.go
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package arithmetic
// greater (>) operator.
type greater struct{}
func (o greater) String() string {
return ">"
}
func (o greater) precedence() uint8 {
return precedenceLowerGreater
}
func (o greater) solve(st *stack) (interface{}, error) {
// Retreive right and left terms.
right, ok := st.pop()
if !ok {
return nil, rightError(o)
}
left, ok := st.pop()
if !ok {
return nil, leftError(o, right)
}
// cast the left and right terms in floats and
// test them.
b, ok := gt(left, right)
if !ok {
return nil, invalidExpressionError(o, left, right)
}
return b, nil
}
type greaterEqual struct{}
// greater or equal (>=) operator.
func (o greaterEqual) String() string {
return ">="
}
func (o greaterEqual) precedence() uint8 {
return precedenceLowerGreater
}
func (o greaterEqual) solve(st *stack) (interface{}, error) {
// Retreive right and left terms.
right, ok := st.pop()
if !ok {
return nil, rightError(o)
}
left, ok := st.pop()
if !ok {
return nil, leftError(o, right)
}
// cast the left and right terms in floats and
// test them.
b, ok := gt(left, right)
if !ok {
return nil, invalidExpressionError(o, left, right)
}
if b {
return true, nil
}
return eq(left, right), nil
}
// lower (<) operator.
type lower struct{}
func (o lower) String() string {
return "<"
}
func (o lower) precedence() uint8 {
return precedenceLowerGreater
}
func (o lower) solve(st *stack) (interface{}, error) {
// Retreive right and left terms.
right, ok := st.pop()
if !ok {
return nil, rightError(o)
}
left, ok := st.pop()
if !ok {
return nil, leftError(o, right)
}
// cast the left and right terms in floats and
// test them.
b, ok := gt(left, right)
if !ok {
return nil, invalidExpressionError(o, left, right)
}
if b {
return false, nil
}
return !eq(left, right), nil
}
// lower or equal (<=) operator.
type lowerEqual struct{}
func (o lowerEqual) String() string {
return "<="
}
func (o lowerEqual) precedence() uint8 {
return precedenceLowerGreater
}
func (o lowerEqual) solve(st *stack) (interface{}, error) {
// Retreive right and left terms.
right, ok := st.pop()
if !ok {
return nil, rightError(o)
}
left, ok := st.pop()
if !ok {
return nil, leftError(o, right)
}
// cast the left and right terms in floats and
// test them.
b, ok := gt(left, right)
if !ok {
return nil, invalidExpressionError(o, left, right)
}
return !b, nil
}