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package expr
import (
"fmt"
)
// EvalProgram returns the result of executing the program with the given resolver.
func EvalProgram(resolver Resolver, program *Program) (v interface{}, err error) {
defer func() {
if r := recover(); r != nil {
if rerr, ok := r.(error); ok {
err = rerr
} else {
panic(r)
}
}
}()
v = evalnode(resolver, program.root).RawValue()
return
}
// Eval returns the result of evaluating the provided expression.
func Eval(resolver Resolver, expr string) (interface{}, error) {
return EvalProgram(resolver, ParseString(expr))
}
func evalnode(resolver Resolver, node node) Value {
switch n := node.(type) {
case identnode:
v := resolver.Resolve(n.ident)
if v == nil {
panic(fmt.Errorf("unresolved name %s", n.ident))
}
return v
case intnode:
if n.sign {
return literalintval(n.ival)
}
return literaluintval(n.uval)
case floatnode:
return literalfloatval(n.fval)
case boolnode:
return literalboolval(n.val)
case strnode:
return literalstrval(n.val)
case runenode:
return literalintval(int64(n.val))
case nilnode:
return literalnilval()
case unaryexpr:
return evalunary(resolver, n)
case binaryexpr:
return evalbinary(resolver, n)
case ternaryexpr:
return evalternary(resolver, n)
default:
panic("invalid node")
}
}
func evalunary(resolver Resolver, node unaryexpr) Value {
n := evalnode(resolver, node.n)
switch node.op {
case unaryplus:
return n
case unarynegate:
return n.Negate()
case unarynot:
return n.Not()
case unarybitnot:
return n.BitNot()
case unaryderef:
return n.Deref()
case unaryref:
return n.Ref()
default:
panic("invalid unary expression")
}
}
func flattengroup(n node) []node {
if n, ok := n.(binaryexpr); ok {
if n.op == binarygroup {
return append(flattengroup(n.a), flattengroup(n.b)...)
}
}
return []node{n}
}
func evalbinary(resolver Resolver, node binaryexpr) Value {
a := evalnode(resolver, node.a)
switch node.op {
case binarymember:
if id, ok := node.b.(identnode); ok {
return a.Dot(id.ident)
}
panic(fmt.Errorf("expected ident node, got %T", node.b))
case binarycall:
in := []Value{}
for _, n := range flattengroup(node.b) {
in = append(in, evalnode(resolver, n))
}
return a.Call(in)
case binarygroup:
return evalnode(resolver, node.b)
}
b := evalnode(resolver, node.b)
switch node.op {
case binarylogicalor:
return a.LogicalOr(b)
case binarylogicaland:
return a.LogicalAnd(b)
case binaryequal:
return a.Equal(b)
case binarynotequal:
return a.NotEqual(b)
case binarylesser:
return a.Lesser(b)
case binarylesserequal:
return a.LesserEqual(b)
case binarygreater:
return a.Greater(b)
case binarygreaterequal:
return a.GreaterEqual(b)
case binaryadd:
return a.Add(b)
case binarysub:
return a.Sub(b)
case binaryor:
return a.Or(b)
case binaryxor:
return a.Xor(b)
case binarymul:
return a.Mul(b)
case binarydiv:
return a.Div(b)
case binaryrem:
return a.Rem(b)
case binarylsh:
return a.Lsh(b)
case binaryrsh:
return a.Rsh(b)
case binaryand:
return a.And(b)
case binaryandnot:
return a.AndNot(b)
case binarysubscript:
return a.Index(b)
default:
panic("invalid binary expression")
}
}
func evalternary(resolver Resolver, node ternaryexpr) Value {
a := evalnode(resolver, node.a).Value().Interface()
cond, ok := a.(bool)
if !ok {
panic(fmt.Errorf("unexpected type %T for ternary", cond))
}
if cond {
return evalnode(resolver, node.b)
}
return evalnode(resolver, node.c)
}
|
