<- Back to shtanton's homepage
aboutsummaryrefslogtreecommitdiff
path: root/subex/parse.go
blob: 24ff3d11b18ff7c3c87549e739e848bbe865311f (plain)
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
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
package subex

import (
	"main/walk"
	"strconv"
	"strings"
)

type RuneReader interface {
	Next() rune
	Rewind()
}

func accept(l RuneReader, chars string) bool {
	r := l.Next()
	for _, char := range chars {
		if char == r {
			return true
		}
	}
	l.Rewind()
	return false
}

func expectBracket(l RuneReader, ifLeft walk.Atom, ifRight walk.Atom) walk.Atom {
	switch l.Next() {
		case '(':
			return ifLeft
		case ')':
			return ifRight
		default:
			panic("Expected ( or )")
	}
}

func isNumericRune(r rune) bool {
	return '0' <= r && r <= '9' || r == '.'
}

// Having just parsed a `, read until the next ` and parse the contents into a list of non-string atoms
func parseNonStringLiteral(l RuneReader) (literals []walk.Atom) {
	for {
		r := l.Next()
		if isNumericRune(r) {
			var builder strings.Builder
			builder.WriteRune(r)
			for {
				r := l.Next()
				if !isNumericRune(r) {
					l.Rewind()
					break
				}
				builder.WriteRune(r)
			}
			numberString := builder.String()
			number, err := strconv.ParseFloat(numberString, 64)
			if err != nil {
				panic("Invalid number literal")
			}
			literals = append(literals, walk.ValueNumber(number))
			continue
		}
		switch r {
			case '`':
				return literals
			case ' ', '\t':
				continue
			case 'n':
				if accept(l, "u") && accept(l, "l") && accept(l, "l") {
					literals = append(literals, walk.ValueNull{})
				} else {
					panic("Invalid literal")
				}
			case 't':
				if accept(l, "r") && accept(l, "u") && accept(l, "e") {
					literals = append(literals, walk.ValueBool(true))
				} else {
					panic("Invalid literal")
				}
			case 'f':
				if accept(l, "a") && accept(l, "l") && accept(l, "s") && accept(l, "e") {
					literals = append(literals, walk.ValueBool(false))
				} else {
					panic("Invalid literal")
				}
			case '{':
				literals = append(literals, walk.MapBegin)
			case '}':
				literals = append(literals, walk.MapEnd)
			case '[':
				literals = append(literals, walk.ArrayBegin)
			case ']':
				literals = append(literals, walk.ArrayEnd)
		}
	}
}

func charIsDigit(c rune) bool {
	return '0' <= c && c <= '9'
}

// Parse a positive integer, reads digits 0-9 and stops at the first non-digit
func parseInt(l RuneReader) (output int) {
	for {
		char := l.Next()
		if charIsDigit(char) {
			output = output * 10 + int(char - '0')
		} else {
			break
		}
	}
	l.Rewind()
	return output
}

// Having just read {, read in and parse the range contents
func parseRepeatRange(l RuneReader) (output []ConvexRange) {
	loop: for {
		var start, end int
		char := l.Next()
		l.Rewind()
		if char == '-' {
			start = -1
		} else {
			start = parseInt(l)
		}
		switch l.Next() {
			case ',':
				output = append(output, ConvexRange{start, start})
				continue loop
			case '-':
				char := l.Next()
				if charIsDigit(char) {
					l.Rewind()
					end = parseInt(l)
				} else {
					l.Rewind()
					end = -1
				}
			case '}':
				output = append(output, ConvexRange{start, start})
				break loop
			default:
				panic("Invalid character in repeat specifier")
		}
		switch l.Next() {
			case ',':
				output = append(output, ConvexRange{start, end})
				continue loop
			case '}':
				output = append(output, ConvexRange{start, end})
				break loop
			default:
				panic("Invalid character in repeat specifier")
		}
	}
	return output
}

func parseReplacement(l RuneReader) (output []OutputContent) {
	// TODO escaping
	loop: for {
		r := l.Next()
		switch r {
			case eof:
				panic("Missing closing \"")
			case '=':
				break loop
			case '$':
				slot := l.Next()
				if slot == eof {
					panic("Missing slot character")
				}
				output = append(output, OutputLoad{slot: slot})
			case '`':
				literals := parseNonStringLiteral(l)
				for _, literal := range literals {
					output = append(output, OutputAtomLiteral {literal})
				}
			case '"':
				output = append(output, OutputAtomLiteral {walk.StringTerminal{}})
			default:
				output = append(output, OutputAtomLiteral{atom: walk.StringAtom(r)})
		}
	}
	return output
}

// Parse the contents of a range subex [] into a map
func parseRangeSubex(l RuneReader) map[walk.Atom]walk.Atom {
	// TODO escaping
	parts := make(map[walk.Atom]walk.Atom)
	var froms []walk.Atom
	var hasTo bool
	for {
		fromsStart := l.Next()
		if fromsStart == ']' {
			hasTo = false
			break
		} else if fromsStart == '=' {
			hasTo = true
			break
		} else if fromsStart == '`' {
			literals := parseNonStringLiteral(l)
			froms = append(froms, literals...)
			continue
		} else if fromsStart == '"' {
			froms = append(froms, walk.StringTerminal{})
			continue
		}
		if accept(l, "-") {
			fromsEnd := l.Next()
			if fromsEnd == ']' || fromsEnd == '=' {
				l.Rewind()
				fromsEnd = fromsStart
			}
			for i := fromsStart; i <= fromsEnd; i += 1 {
				froms = append(froms, walk.StringAtom(i))
			}
		} else {
			froms = append(froms, walk.StringAtom(fromsStart))
		}
	}
	if len(froms) == 0 {
		panic("Missing from part of range expression")
	}

	var tos []walk.Atom
	if hasTo {
		for {
			tosStart := l.Next()
			if tosStart == ']' {
				break
			} else if tosStart == '`' {
				literals := parseNonStringLiteral(l)
				tos = append(tos, literals...)
				continue
			} else if tosStart == '"' {
				tos = append(tos, walk.StringTerminal{})
				continue
			}
			if accept(l, "-") {
				tosEnd := l.Next()
				if tosEnd == ']' {
					l.Rewind()
					tosEnd = tosStart
				}
				for i := tosStart; i <= tosEnd; i += 1 {
					tos = append(tos, walk.StringAtom(i))
				}
			} else {
				tos = append(tos, walk.StringAtom(tosStart))
			}
		}
	} else {
		tos = froms
	}
	if len(tos) == 0 {
		panic("Missing to part of range expression")
	}
	
	for i, from := range froms {
		parts[from] = tos[i % len(tos)]
	}
	return parts
}

func parseSubex(l RuneReader, minPower int) SubexAST {
	var lhs SubexAST
	r := l.Next()
	switch r {
		case eof:
			return nil
		case '(':
			lhs = parseSubex(l, 0)
			if !accept(l, ")") {
				panic("Missing matching )")
			}
		case '[':
			rangeParts := parseRangeSubex(l)
			lhs = SubexASTRange {rangeParts}
		case ')', '|', ';', '{', '+', '-', '*', '/', '$':
			l.Rewind()
			return nil
		case '=':
			replacement := parseReplacement(l)
			lhs = SubexASTOutput{replacement}
		case '.':
			lhs = SubexASTCopyAny{}
		case '"':
			lhs = SubexASTCopyAtom {walk.StringTerminal{}}
		case '`':
			literals := parseNonStringLiteral(l)
			lhs = SubexASTEmpty{}
			for _, literal := range literals {
				lhs = SubexASTConcat {lhs, SubexASTCopyAtom {literal}}
			}
		default:
			lhs = SubexASTCopyAtom{atom: walk.StringAtom(r)}
	}
	loop: for {
		if minPower <= 0 {
			next := parseSubex(l, 1)
			if next != nil {
				lhs = SubexASTConcat{lhs, next}
				continue loop
			}
		}
		r := l.Next()
		switch {
			case r == '{' && minPower <= 8:
				lhs = SubexASTRepeat {
					content: lhs,
					acceptable: parseRepeatRange(l),
				}
			case r == '+' && minPower <= 8:
				lhs = SubexASTSum {lhs}
			case r == '*' && minPower <= 8:
				lhs = SubexASTProduct {lhs}
			case r == '-' && minPower <= 8:
				lhs = SubexASTNegate {lhs}
			case r == '/' && minPower <= 8:
				lhs = SubexASTReciprocal {lhs}
			case r == '!' && minPower <= 8:
				lhs = SubexASTNot {lhs}
			case r == '$' && minPower <= 8:
				slot := l.Next()
				if slot == eof {
					panic("Missing slot character")
				}
				lhs = SubexASTStore{
					match: lhs,
					slot: slot,
				}
			case r == '|' && minPower <= 4:
				rhs := parseSubex(l, 5)
				if rhs == nil {
					panic("Missing subex after |")
				}
				lhs = SubexASTOr{lhs, rhs}
			case r == ';' && minPower <= 2:
				rhs := parseSubex(l, 3)
				if rhs == nil {
					panic("Missing subex after ;")
				}
				lhs = SubexASTJoin{
					content: lhs,
					delimiter: rhs,
				}
			default:
				l.Rewind()
				break loop
		}
	}
	return lhs
}

func Parse(l RuneReader) SubexAST {
	ast := parseSubex(l, 0)
	if ast == nil {
		return SubexASTEmpty{}
	}
	return ast
}