1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
package subex
import (
"main/walk"
)
// Where slots are stored
type Store map[rune][]walk.Atom
// Return a new store with all the data from this one
func (store Store) clone() Store {
newStore := make(Store)
for key, val := range store {
newStore[key] = val
}
return newStore
}
// Return a copy of this store but with an additional slot set
func (store Store) withValue(key rune, value []walk.Atom) Store {
newStore := store.clone()
newStore[key] = value
return newStore
}
// Compile the SubexAST into a transducer SubexState that can be run
func CompileTransducer(transducerAst SubexAST) SubexState {
return transducerAst.compileWith(&SubexNoneState{})
}
// An immutable stack for outputting to
type OutputStack struct {
head []walk.Atom
tail *OutputStack
}
func (stack OutputStack) pop() ([]walk.Atom, OutputStack) {
return stack.head, *stack.tail
}
func (stack OutputStack) push(atoms []walk.Atom) OutputStack {
return OutputStack {
head: atoms,
tail: &stack,
}
}
func (stack OutputStack) replace(atoms []walk.Atom) OutputStack {
return OutputStack {
head: atoms,
tail: stack.tail,
}
}
func (stack OutputStack) peek() []walk.Atom {
return stack.head
}
func topAppend(outputStack OutputStack, atoms []walk.Atom) OutputStack {
head := outputStack.peek()
return outputStack.replace(walk.ConcatData(head, atoms))
}
// One branch of subex execution
type SubexBranch struct {
// Content of slots in this branch
store Store
// State in this branch
state SubexState
// The output stack. At the end of the program, whatever is on top of this will be output
// States may push or pop to the stack as they wish, creating sort of a call stack that allows states to capture the output of other states
outputStack OutputStack
}
// Read a single character and return all the branches resulting from this branch consuming it
func (pair SubexBranch) eat(char walk.Atom) []SubexBranch {
return pair.state.eat(pair.store, pair.outputStack, char)
}
func (pair SubexBranch) accepting() []OutputStack {
return pair.state.accepting(pair.store, pair.outputStack)
}
func equalStates(left SubexBranch, right SubexBranch) bool {
// Only care about if they are the same pointer
return left.state == right.state
}
// If two branches have the same state, only the first has a chance of being successful
// This function removes all of the pointless execution branches to save execution time
func pruneStates(states []SubexBranch) (newStates []SubexBranch) {
outer: for _, state := range states {
for _, newState := range newStates {
if equalStates(state, newState) {
continue outer
}
}
newStates = append(newStates, state)
}
return newStates
}
// Run the subex transducer
func RunTransducer(transducer SubexState, input []walk.Atom) (output []walk.Atom, err bool) {
states := []SubexBranch{{
state: transducer,
outputStack: OutputStack {
head: nil,
tail: nil,
},
store: make(Store),
}}
for _, piece := range input {
var newStates []SubexBranch
for _, state := range states {
newStates = append(newStates, state.eat(piece)...)
}
states = pruneStates(newStates)
if len(states) == 0 {
return nil, true
}
}
for _, state := range states {
acceptingStacks := state.accepting()
for _, stack := range acceptingStacks {
output := stack.head
return output, false
}
}
return nil, true
}
|
