在Go中评估公式

Question

Using Go (golang) I'd like to take a string with a formula and evaluate it with pre-defined values. Here's a way to do it with python's parser module:

x = 8
code = parser.expr("(x + 2) / 10").compile()
print eval(code)
# prints 1

Any idea how to do it with Go?

Answer 1

You will probably need to resort to a library that interprets math statements or have to write your own parser. Python being a dynamic language can parse and execute python code at runtime. Standard Go cannot do that.

If you want to write a parser on your own, the go package will be of help. Example (On play):

import (
    "go/ast"
    "go/parser"
    "go/token"
)

func main() {
    fs := token.NewFileSet()
    tr, _ := parser.ParseExpr("(3-1) * 5")
    ast.Print(fs, tr)
}

The resulting AST (Abstract Syntax Tree) can then be traversed and interpreted as you choose (handling '+' tokens as addition for the now stored values, for example).