mirror of
https://github.com/gopl-zh/gopl-zh.github.com.git
synced 2024-11-25 07:38:57 +00:00
53 lines
940 B
Go
53 lines
940 B
Go
|
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
|
||
|
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
||
|
|
|
||
|
|
package eval
|
||
|
|
|
||
|
|
import (
|
||
|
|
"bytes"
|
||
|
|
"fmt"
|
||
|
|
)
|
||
|
|
|
||
|
|
// Format formats an expression as a string.
|
||
|
|
// It does not attempt to remove unnecessary parens.
|
||
|
|
func Format(e Expr) string {
|
||
|
|
var buf bytes.Buffer
|
||
|
|
write(&buf, e)
|
||
|
|
return buf.String()
|
||
|
|
}
|
||
|
|
|
||
|
|
func write(buf *bytes.Buffer, e Expr) {
|
||
|
|
switch e := e.(type) {
|
||
|
|
case literal:
|
||
|
|
fmt.Fprintf(buf, "%g", e)
|
||
|
|
|
||
|
|
case Var:
|
||
|
|
fmt.Fprintf(buf, "%s", e)
|
||
|
|
|
||
|
|
case unary:
|
||
|
|
fmt.Fprintf(buf, "(%c", e.op)
|
||
|
|
write(buf, e.x)
|
||
|
|
buf.WriteByte(')')
|
||
|
|
|
||
|
|
case binary:
|
||
|
|
buf.WriteByte('(')
|
||
|
|
write(buf, e.x)
|
||
|
|
fmt.Fprintf(buf, " %c ", e.op)
|
||
|
|
write(buf, e.y)
|
||
|
|
buf.WriteByte(')')
|
||
|
|
|
||
|
|
case call:
|
||
|
|
fmt.Fprintf(buf, "%s(", e.fn)
|
||
|
|
for i, arg := range e.args {
|
||
|
|
if i > 0 {
|
||
|
|
buf.WriteString(", ")
|
||
|
|
}
|
||
|
|
write(buf, arg)
|
||
|
|
}
|
||
|
|
buf.WriteByte(')')
|
||
|
|
|
||
|
|
default:
|
||
|
|
panic(fmt.Sprintf("unknown Expr: %T", e))
|
||
|
|
}
|
||
|
|
}
|