85 lines
2.4 KiB
Go
85 lines
2.4 KiB
Go
/* SHS: Syntactically Homogeneous Shell
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* Copyright (C) 2019 Aidan Hahn
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package ast
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import "gitlab.com/whom/shs/log"
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func (t *Token) Eval(funcs FuncTable, vars VarTable) (*Token, bool) {
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if t == nil {
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return nil, false
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}
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var reduce func(*Token) *Token
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reduce = func(t_ *Token) *Token {
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var unwrap bool
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if t_.Next != nil {
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t_.Next = reduce(t_.Next)
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}
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switch (t_.Tag) {
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case SYMBOL:
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maybeToken := GetVar(t_.Inner.(string), vars)
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if maybeToken != nil {
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tok, _ := maybeToken.Eval(funcs, vars)
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tok.Next = t_.Next
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return tok
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}
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case LIST:
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t_.Inner, unwrap = t_.Inner.(*Token).Eval(funcs, vars)
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if unwrap {
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next := t_.Next
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t_ = t_.Inner.(*Token)
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if t_ == nil {
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log.Log(log.DEBUG, "nil Inner on list unwrap", "eval")
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return nil
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}
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i := &t_
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for (*i).Next != nil {
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i = &((*i).Next)
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}
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(*i).Next = next
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}
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}
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return t_
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}
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ret := reduce(t)
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if ret == nil {
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log.Log(log.INFO, "reduce returned nil", "eval")
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return nil, false
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}
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if ret.Tag == SYMBOL {
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f := GetFunction(ret.Inner.(string), funcs)
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if f == nil {
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log.Log(log.DEBUG,
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"could not find definition for symbol " + ret.Inner.(string),
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"eval")
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return nil, false
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}
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return (*f).CallFunction(ret.Next, vars, funcs), true
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}
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return ret, false
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}
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