├── .gitignore ├── LICENSE ├── README.md ├── ansi.py ├── assembler.py ├── both.py ├── finite.py ├── hal-100.md ├── hal_vm.py ├── hal_watch.py ├── literals.py ├── literals_hal.py ├── plus.py ├── plus_compiled.py ├── regex_parse.py ├── star.py ├── star_compiled.py └── tests.py /.gitignore: -------------------------------------------------------------------------------- 1 | *.py[cod] 2 | 3 | # C extensions 4 | *.so 5 | 6 | # Packages 7 | *.egg 8 | *.egg-info 9 | dist 10 | build 11 | eggs 12 | parts 13 | bin 14 | var 15 | sdist 16 | develop-eggs 17 | .installed.cfg 18 | lib 19 | lib64 20 | 21 | # Installer logs 22 | pip-log.txt 23 | 24 | # Unit test / coverage reports 25 | .coverage 26 | .tox 27 | nosetests.xml 28 | 29 | # Translations 30 | *.mo 31 | 32 | # Mr Developer 33 | .mr.developer.cfg 34 | .project 35 | .pydevproject 36 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. {http://fsf.org/} 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | {one line to give the program's name and a brief idea of what it does.} 635 | Copyright (C) {year} {name of author} 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see {http://www.gnu.org/licenses/}. 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | regexercise_solutions Copyright (C) 2013 Darius Bacon 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | {http://www.gnu.org/licenses/}. 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | {http://www.gnu.org/philosophy/why-not-lgpl.html}. 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | regexercise 2 | =========== 3 | 4 | ### Exercises in implementing regular-expression search 5 | 6 | Let's say you know what a [regular 7 | expression](http://en.wikipedia.org/wiki/Regular_expression) is, 8 | you're a fairly experienced programmer, and you'd like to reach a 9 | deeper understanding (or just have some fun) by writing a matcher for 10 | them. These problems gradually work up to a compiled matcher, without 11 | telling you how to do it. Each has a solution in a page or less of 12 | Python, using no especially advanced Python features. 13 | 14 | I'm confident my solutions are worth reading; on the other hand, I 15 | have no idea whether this sequence of problems offered without telling 16 | you the algorithm makes an effective way to learn; if you tackle this, 17 | please tell me how it goes. ([Comment 18 | here](https://github.com/darius/regexercise/issues) or email 19 | withal@gmail.com.) 20 | 21 | To start: `pip install peglet`, read the first problem below, edit 22 | [literals.py](literals.py), then run `python tests.py` until it likes 23 | your solution. The code is known to work in Python 2.7 and Python 24 | 3.2, and expected to work in 2.6 and up. 25 | 26 | ## The problems 27 | 28 | **Literal patterns**: Given a list of strings and a stream of 29 | characters, report whether the stream starts with one of the 30 | strings. (You don't have to say which one.) For example, in Python we 31 | might ask 32 | 33 | >>> stream = iter('cats are fat') 34 | >>> search(['rat', 'cat'], stream) # Does 'rat' or 'cat' start the stream? 35 | True 36 | >>> ''.join(stream) # The rest wasn't consumed, see: 37 | 's are fat' 38 | 39 | The last line shows that we want the match reported as soon as it's 40 | complete, without reading the rest of the stream; so we couldn't 41 | implement `search` as 42 | 43 | def search(strings, chars): 44 | chars = ''.join(chars) 45 | return any(chars.startswith(string) for string in strings) 46 | 47 | because that would eat all the input before checking for any 48 | match. (If the input *doesn't* match any of the strings, you can 49 | report that as soon as it's evident, but you don't have to; the tests 50 | only check that you return False then, not how much of the stream you 51 | consume.) 52 | 53 | Test your solution by defining it in a module [literals.py](literals.py). Then 54 | 55 | $ python tests.py 56 | 57 | will check it. You can run just the literals tests via 58 | 59 | $ python tests.py literals 60 | 61 | or 62 | 63 | >>> import tests, literals 64 | >>> tests.check_literals(literals) 65 | 'Literal patterns: all tests passed.' 66 | 67 | **Abstract data**: As before, but instead of a list of strings, we 68 | take a restricted kind of regular expression. You can represent these 69 | expressions however you like; define three constructors: 70 | 71 | * `literal(character)` should represent a regex matching just that character. 72 | * `either(regex1, regex2)` should match what either regex1 or 73 | regex2 matches; i.e. it represents `regex1|regex2`. 74 | * `chain(regex1, regex2)` matches a match of `regex1` followed 75 | by a match of `regex2`; i.e. it represents `regex1 regex2`. 76 | 77 | So you could encode the same pattern as before as 78 | 79 | >>> def sequence(regexes): return reduce(chain, regexes) 80 | >>> rat_or_cat = either(sequence(map(literal, 'rat')), sequence(map(literal, 'cat'))) 81 | 82 | and then, with your new search function, `search(rat_or_cat, stream)` 83 | should produce the same result. Of course one way to solve this is, 84 | just expand the pattern into a list of strings and leave `search` 85 | unchanged. But this list of strings could get exponentially bigger 86 | than the regular expression -- consider 87 | 88 | >>> bit = either(literal('0'), literal('1')) 89 | >>> ten_bits = sequence(10 * [bit]) 90 | 91 | `ten_bits`, a regex with 20 literals, would expand out to a list of 92 | 1024 strings; and growing from 10 to 30 would expand the strings to 93 | over a billion. (Also, we're soon going to add in a repetition 94 | operator that'd make the set of matching strings infinite.) So now you 95 | want to work with a more tailored representation. 96 | 97 | Put your code in [finite.py](finite.py) so [tests.py](tests.py) 98 | knows where to find it. 99 | 100 | **Repetition**: Now in [plus.py](plus.py) with one more 101 | regex constructor: 102 | 103 | * `plus(regex)` has matches consisting of 1 or more matches of `regex` 104 | in sequence. (The Kleene plus: `(regex)+` in the usual notation.) 105 | 106 | The following two problems could be tackled in either order. 107 | 108 | **Matching nothing**: In [star.py](star.py) add the 109 | `star` constructor, like `plus` but matching 0 or more. Getting the 110 | matching to terminate may be tricky for patterns like 111 | `star(star(regex))`. 112 | 113 | **Compiling**: In [plus_compiled.py](plus_compiled.py) or 114 | [star_compiled.py](star_compiled.py): Don't allocate any memory inside 115 | the main matching loop. (Some languages would make satisfying the 116 | letter of this requirement more painful than it's worth; so it's 117 | enough if there's an obvious translation into an allocation-free loop 118 | in a lower-level language.) 119 | 120 | **Machine code for literal patterns**: In 121 | [literals_hal.py](literals_hal.py). Take literal patterns, as in the 122 | first problem, but before the start of matching compile them into a 123 | machine-code program that'll do the matching. I've defined a simple 124 | target machine for this, the [HAL 100](hal-100.md), since the IBM 7094 125 | that Thompson used was kind of tricky and obscure. 126 | 127 | **Machine code**: As above, but for regular expressions. You might 128 | jump straight to this problem if you're confident and impatient. 129 | 130 | **Bonus:** In [both.py](both.py) add a `both(regex1, regex2)` 131 | constructor that matches when both of its arguments match. 132 | 133 | ## General hints 134 | 135 | For all these problems you can keep a set of states of some kind; in 136 | the main loop you ask if any of the states means a match, and if not, 137 | get the next character from the stream and update the state-set 138 | according to it. For the first problem [here's 139 | pseudocode](http://stackoverflow.com/a/846728/27024) (in the first 140 | part of the answer; it assumes there's just one pattern string, and 141 | searches for it anywhere in the input, not just at the beginning, 142 | but it gives the idea). 143 | 144 | What kind of states will work for the subsequent problems? 145 | Essentially, regular expressions again: if a state represents a 146 | regular expression r, and you get input character c, then the 147 | [Brzozowski 148 | derivative](http://blog.sigfpe.com/2005/05/derivatives-of-regular-expressions.html) 149 | dr/dc is the next state. Thompson represents dr/dc as a set of 150 | possible next states, zero or more of them. If r is `ax|ay` and c is 151 | `a`, then you could get either one next state, `x|y`, or two next 152 | states, `x` and `y`, depending on how you write your code. 153 | 154 | Here's the original paper ["Regular Expression Search 155 | Algorithm"](http://www.fing.edu.uy/inco/cursos/intropln/material/p419-thompson.pdf). 156 | -------------------------------------------------------------------------------- /ansi.py: -------------------------------------------------------------------------------- 1 | """ 2 | ANSI terminal control 3 | XXX copy me to: 4 | /home/darius/oldgit/spaced-out/deck-player/ansi.py 5 | /home/darius/oldgit/spellmell/ansi.py 6 | """ 7 | 8 | prefix = '\x1b[' 9 | 10 | home = prefix + 'H' 11 | clear_to_bottom = prefix + 'J' 12 | clear_screen = prefix + '2J' + home 13 | clear_to_eol = prefix + 'K' 14 | 15 | save_cursor_pos = prefix + 's' 16 | restore_cursor_pos = prefix + 'u' 17 | 18 | show_cursor = prefix + '?25h' 19 | hide_cursor = prefix + '?25l' 20 | 21 | def goto(x, y): 22 | return prefix + ('%d;%dH' % (y, x)) 23 | 24 | black, red, green, yellow, blue, magenta, cyan, white = range(8) 25 | 26 | def bright(color): 27 | return 60 + color 28 | 29 | def set_foreground(color): 30 | return (prefix + '%dm') % (30 + color) 31 | 32 | def set_background(color): 33 | return (prefix + '%dm') % (40 + color) 34 | -------------------------------------------------------------------------------- /assembler.py: -------------------------------------------------------------------------------- 1 | """ 2 | Generic 2-pass assembler. 3 | """ 4 | 5 | from collections import defaultdict 6 | 7 | def assemble(assemble1, lines, env, origin=0): 8 | lines = list(lines) 9 | forward_refs = defaultdict(int) 10 | both = UnionDict(env, forward_refs) 11 | assembler_pass(assemble1, lines, both, origin) 12 | unresolved = set(forward_refs) - set(env) 13 | if unresolved: 14 | raise Exception("Unresolved refs", ' '.join(sorted(unresolved))) 15 | return assembler_pass(assemble1, lines, env, origin) 16 | 17 | class UnionDict(object): # XXX rename 18 | def __init__(self, dict1, dict2): 19 | self.dict1, self.dict2 = dict1, dict2 20 | def __getitem__(self, key): 21 | try: 22 | return self.dict1[key] 23 | except KeyError: 24 | return self.dict2[key] 25 | def __setitem__(self, key, value): 26 | self.dict1[key] = value 27 | def get(self, key, default=None): 28 | return self.dict1.get(key, default) 29 | 30 | def assembler_pass(assemble1, lines, env, origin): 31 | cells = [] 32 | for line in lines: 33 | here = origin + len(cells) 34 | label, tokens = tokenize(line) 35 | if label: 36 | if env.get(label, here) != here: 37 | raise Exception("Multiply-defined", label, env[label], here) 38 | env[label] = here 39 | if not tokens: 40 | continue 41 | env['__here__'] = here 42 | cells.extend(assemble1(tokens, env)) 43 | return cells 44 | 45 | def starts_comment(string): 46 | return string.startswith(';') 47 | 48 | def tokenize(line): 49 | tokens = line.split() 50 | if not line or line[:1].isspace() or starts_comment(line): 51 | label = '' 52 | else: 53 | label = tokens.pop(0) 54 | for i, token in enumerate(tokens): 55 | if starts_comment(token): 56 | tokens = tokens[:i] 57 | break 58 | return label, tokens 59 | -------------------------------------------------------------------------------- /both.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | """ 4 | 5 | def search(re, chars): 6 | """Given a regular expression and an iterator of chars, return True if 7 | re matches some prefix of ''.join(chars); but only consume chars 8 | up to the end of the match.""" 9 | raise NotImplementedError 10 | 11 | # Regular-expression constructors; the re above is built by these. 12 | # Feel free to change these definitions if it helps. 13 | def literal(char): return ('literal', char, None) 14 | def chain(re1, re2): return ('chain', re1, re2) 15 | def either(re1, re2): return ('either', re1, re2) 16 | def both(re1, re2): return ('both', re1, re2) 17 | def star(re): return ('star', re, None) 18 | -------------------------------------------------------------------------------- /finite.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | """ 4 | 5 | def search(re, chars): 6 | """Given a regular expression and an iterator of chars, return True if 7 | re matches some prefix of ''.join(chars); but only consume chars 8 | up to the end of the match.""" 9 | raise NotImplementedError 10 | 11 | # Regular-expression constructors; the re above is built by these. 12 | # Feel free to change these definitions if it helps. 13 | def literal(char): return ('literal', char, None) 14 | def chain(re1, re2): return ('chain', re1, re2) 15 | def either(re1, re2): return ('either', re1, re2) 16 | -------------------------------------------------------------------------------- /hal-100.md: -------------------------------------------------------------------------------- 1 | ## The HAL 100 2 | 3 | This is a toy computer designed to make its running easy to follow, 4 | with 100 words of main memory, 9 general-purpose registers, and 10 5 | instructions. Here's a short example program in assembly language: 6 | 7 | ;; Comments start with semicolons. 8 | set r9,,1 ; r9 = 1; 9 | loop getch r1 ; loop: r1 = getchar(); 10 | ifeq r1,'X',done ; if (r1 == 'X') goto done; 11 | add r9,,1 ; r9 += 1; 12 | jump ,,loop ; goto loop; 13 | done halt ; done: exit(0); 14 | 15 | The comments on the right give an almost-equivalent C program. 16 | 17 | Every instruction takes three arguments. For example, 18 | 19 | ifeq r1,'X',done 20 | 21 | with `r1`, `'X'`, and `done`, takes the value of register 1, compares it to 22 | the literal character `X`, and jumps to the instruction at `done` if they're 23 | equal. On the other hand, in 24 | 25 | set r9,,1 26 | 27 | the second argument, left out, has a default of 0. (We'll see below 28 | how a non-default value would affect this instruction.) In 29 | 30 | getch r1 31 | 32 | only the first argument is supplied. (`getch` would ignore the other 33 | two if they were there, as it happens.) 34 | 35 | Each instruction gets encoded in one word of memory. In modern 36 | computers words are in binary, e.g. 32 or 64 bits; but the HAL 100 has 37 | words of 9 characters instead. For example, the assembly language 38 | 39 | ifeq r1,'X',done 40 | 41 | becomes the machine-code word `ifeq 1X34` if `done` happens to be 42 | defined as address `34`. I should maybe apologize for this design; 43 | it's meant to help you follow the execution of self-modifying code 44 | without an intervening layer of interpretation. The IBM 7094 of 45 | Thompson's paper had a fairly similar instruction set, but with many 46 | more instructions, in a conventional binary encoding. If you're 47 | comfortable writing assembly code for another architecture, such as 48 | x86 or ARM, you might prefer targeting that instead. 49 | 50 | 51 | ## Running a program 52 | 53 | Besides being a stub for one of the exercises, 54 | [literals_hal.py](literals_hal.py) shows how to run a HAL-100 assembly 55 | program. In a terminal window, enter 56 | 57 | python literals_hal.py 58 | 59 | The screen will show the state of the machine before executing each 60 | instruction. Hit the enter key to step forward to the next 61 | instruction. (XXX explain the screen) 62 | 63 | If you have an assembly-language program in a file `myprogram.s`, you 64 | can run it the same way with 65 | 66 | python hal_watch.py myprogram.s "my input" 67 | 68 | ## The instructions 69 | 70 | ### set 71 | 72 | set dest_register,source_register,constant 73 | 74 | is like the C 75 | 76 | dest_register = source_register + constant 77 | 78 | In our example 79 | 80 | set r9,,1 81 | 82 | `dest_register` is 9, `source_register` is 0, and `literal` is 83 | 1. Register 0 is always treated specially (for all instructions): its 84 | value is 0, and assignments to it have no effect. 85 | 86 | Arithmetic on this machine is in decimal, with numbers from 0 to 99. A 87 | register, like a machine word, is a 9-character string; the two 88 | rightmost characters hold the decimal number, while the 7 characters 89 | to the left get filled in from whichever of the addends is nonblank, 90 | if any. The literal can be negative, so to subtract 1 from `r9` you could 91 | 92 | set r9,r9,-1 93 | 94 | It's an error to have non-digits in the number field (except for the 95 | minus sign). 96 | 97 | ### add 98 | 99 | set dest_register,source_register,constant 100 | 101 | is like the C 102 | 103 | dest_register += source_register + constant 104 | 105 | except with addition defined as above. 106 | 107 | ### fetch 108 | 109 | fetch dest_register,address_register,constant 110 | 111 | means 112 | 113 | dest_register = memory[address_register + constant] 114 | 115 | where the subscript takes the address from the 2 decimal digits of 116 | `address_register + constant`, and, as always, addition is decimal as 117 | above. 118 | 119 | ### store 120 | 121 | store value_register,address_register,constant 122 | 123 | means 124 | 125 | memory[address_register + constant] = value_register 126 | 127 | ### jump 128 | 129 | jump return_register,address_register,constant 130 | 131 | serves for goto, subroutine call, and return. It sets 132 | `return_register` to the address following the current instruction, 133 | then jumps to the address `address_register + constant`. (As always, 134 | if `return_register` is the 0 default, setting it has no effect; so 135 | that'd make a normal goto.) Here's an example call and return, plus a 136 | goto at the start to skip around the subroutine: 137 | 138 | jump ,,after 139 | sub1 add r1,,-1 ; subtract 1 from r1 140 | jump ,r9 ; return 141 | after set r1,,5 142 | jump r9,,sub1 ; call sub1 143 | ;; now r1 == 4 144 | 145 | ### ifeq 146 | 147 | This is explained in the example at top. Note that unlike all the 148 | other instructions we've seen so far, the second argument is not a 149 | register number, it's a literal character. 150 | 151 | ### ifne 152 | 153 | Like ifeq, but compare for not-equal instead of for equal. 154 | 155 | ### getch 156 | 157 | getch dest_register 158 | 159 | reads the next character of input, if any, and sets dest_register to 160 | it. On end-of-input it halts immediately, as if with a halt 161 | instruction with a 0 argument. (The Halt exception returned to the 162 | host environment also carries an argument saying "Out of input".) 163 | 164 | ### halt 165 | 166 | halt ignored,register,constant 167 | 168 | Halt execution, returning `register+constant` to the host environment. 169 | In our exercises, a return value of 0 is taken to mean the input did 170 | not match, while nonzero means it did match. 171 | 172 | ### noop 173 | 174 | Do nothing. (The 5-character machine-code mnemonic for this 175 | instruction is all spaces. But you can write `noop` if you prefer.) 176 | -------------------------------------------------------------------------------- /hal_vm.py: -------------------------------------------------------------------------------- 1 | """ 2 | A virtual machine meant to share enough of the IBM 7094's character to 3 | run Thompson's code in an obvious direct translation, but to be easier 4 | to quickly explain and visually animate. So the 'machine words' are 5 | fixed-length strings with fields holding instruction mnemonics and 6 | decimal numbers. 7 | """ 8 | 9 | import assembler 10 | import re 11 | 12 | ## v = load('catfind.s', '') 13 | ## v.show() 14 | #. 0 r2 r4 r6 r8 15 | #. r1 r3 r5 r7 r9 16 | #. 17 | #. 0 start ==>set 4 0 20 20 40 60 ifne 1 C 13 80 18 | #. 3 advance 1 set 6 0 40 21 41 61 jump 9 0 11 81 19 | #. 11 next 2 set 7 0 40 22 42 62 ifne 1 A 13 82 20 | #. 13 fail 3 set 2 0 3 23 43 63 jump 9 0 11 83 21 | #. 20 states1 4 store 2 7 0 24 44 64 ifne 1 T 13 84 22 | #. 40 states2 5 set 7 4 0 25 45 65 found 0 0 0 85 23 | #. 60 code 6 set 4 6 0 26 46 66 86 24 | #. 7 set 6 7 0 27 47 67 87 25 | #. 8 getch 1 0 0 28 48 68 88 26 | #. 9 set 8 4 0 29 49 69 89 27 | #. 10 jump 0 0 60 30 50 70 90 28 | #. 11 store 9 7 0 31 51 71 91 29 | #. 12 set 7 7 1 32 52 72 92 30 | #. 13 fetch 2 8 0 33 53 73 93 31 | #. 14 set 8 8 1 34 54 74 94 32 | #. 15 jump 0 2 0 35 55 75 95 33 | #. 16 36 56 76 96 34 | #. 17 37 57 77 97 35 | #. 18 38 58 78 98 36 | #. 19 39 59 79 99 37 | #. 38 | 39 | def toplevel(filename, inputs=''): 40 | vm = load(filename, inputs) 41 | vm.show() 42 | 43 | def load(filename, inputs): 44 | return load_program(open(filename), inputs) 45 | 46 | def load_program(program_lines, inputs): 47 | env = dict(('r%d'%i, i) for i in range(1, 10)) 48 | words = assembler.assemble(assemble1, program_lines, env) 49 | return VM(words, inputs, env) 50 | 51 | def assemble1(tokens, env): 52 | "Assemble a single line of source code." 53 | mnemonic, rest = tokens[0].lower(), ' '.join(tokens[1:]) 54 | fields = [field.strip() or '0' for field in rest.split(',')] 55 | args = [eval(operand, {}, env) for operand in fields] 56 | if mnemonic == 'zeroes': 57 | assert len(args) == 1 58 | return [' '*9] * args[0] 59 | else: 60 | while len(args) < 3: 61 | args.append('0') 62 | assert len(args) == 3 63 | return ['%-5s%s%s%02s' % (mnemonic, args[0], args[1], int(args[2]))] 64 | 65 | def show_env(env): 66 | return ['%2d %-12s' % (value, label) 67 | for label, value in sorted(env.items(), key=lambda kv: kv[1]) 68 | if not re.match(r'r[1-9]|__here__', label)] 69 | 70 | def put_number(vh, vn): 71 | assert len(vh) == 7 72 | assert isinstance(vn, int) 73 | vl = '%2d' % vn 74 | assert len(vl) == 2, vn 75 | return vh + vl 76 | 77 | def get_number(v): 78 | assert len(v) == 9 79 | vh, vl = v[:7], v[7:] 80 | assert len(vl) == 2, repr(v) 81 | return vh, int('0' if vl == ' ' else vl) 82 | 83 | def add(u, v): 84 | uh, un = get_number(u) 85 | vh, vn = get_number(v) 86 | rn = (un + vn + 100) % 100 87 | if not uh.strip(): return put_number(vh, rn) 88 | if not vh.strip(): return put_number(uh, rn) 89 | assert False 90 | ## add(' '*7+' 1', ' '*7+'-1') 91 | #. ' 0' 92 | 93 | class VM(object): 94 | 95 | def __init__(self, program, input_chars, env): 96 | self.pc = put_number(' '*7, 0) 97 | self.M = [' '*9] * 100 98 | self.R = [' '*8+'0'] + [' '*9] * 9 99 | self.input_chars = iter(input_chars) 100 | self.env = env 101 | for addr, value in enumerate(program): 102 | assert len(value) == 9 103 | self.store(put_number(' '*7, addr), value) 104 | 105 | def show(self): 106 | regs = map(self.show_reg, range(10)) 107 | print('\n'.join(format_columns(regs, 5))) 108 | print('') 109 | defs = pad(show_env(self.env), 20) 110 | insns = map(self.show_cell, range(100)) 111 | print('\n'.join(format_columns(defs + list(insns), 6))) 112 | 113 | def show_reg(self, i): 114 | r = ' ' if i == 0 else 'r%d' % i 115 | word = self.R[i] 116 | return '%s %s %s %s %s' % (r, word[:5], word[5], word[6], word[7:]) 117 | 118 | def show_cell(self, i): 119 | word = self.M[i] 120 | addr = '==>' if i == get_number(self.pc)[1] else '%2d ' % i 121 | return '%s%s %s %s %s' % (addr, word[:5], word[5], word[6], word[7:]) 122 | 123 | def fetch(self, addr): 124 | ah, an = get_number(addr) 125 | return self.M[an] 126 | 127 | def store(self, addr, value): 128 | ah, an = get_number(addr) 129 | self.M[an] = value 130 | 131 | def get(self, r): 132 | return self.R[int(r)] 133 | 134 | def set(self, r, value): 135 | if int(r) != 0: 136 | self.R[int(r)] = value 137 | 138 | def run(self): 139 | while True: 140 | try: 141 | self.step() 142 | except Halt as e: 143 | return e.args[0] 144 | 145 | def step(self): 146 | insn = self.fetch(self.pc) 147 | self.pc = add(self.pc, put_number(' '*7, 1)) 148 | op, r1, r2, addr = insn[:5], insn[5], insn[6], insn[7:] 149 | 150 | def ea(): 151 | return add(self.get(r2), ' '*7 + addr) 152 | 153 | if op == 'fetch': 154 | self.set(r1, self.fetch(ea())) 155 | elif op == 'store': 156 | self.store(ea(), self.get(r1)) 157 | elif op == 'set ': 158 | self.set(r1, ea()) 159 | elif op == 'add ': 160 | self.set(r1, add(self.get(r1), ea())) 161 | elif op == 'jump ': 162 | self.set(r1, self.pc) 163 | self.pc = ea() 164 | elif op == 'ifeq ': 165 | value = ' '*8 + r2 166 | if self.get(r1) == value: 167 | self.pc = ' '*7 + addr 168 | elif op == 'ifne ': 169 | value = ' '*8 + r2 170 | if self.get(r1) != value: 171 | self.pc = ' '*7 + addr 172 | elif op == 'getch': 173 | ch = next(self.input_chars, None) 174 | if ch is None: 175 | raise Halt(0, 'Out of input') 176 | self.set(r1, ' '*8 + ch) 177 | elif op == 'noop ' or op == ' ': 178 | pass 179 | elif op == 'halt ': 180 | value = ea() 181 | raise Halt(value, 'Found' if value else 'Not found') 182 | else: 183 | assert False, "Unknown instruction: %r" % op 184 | 185 | class Halt(Exception): pass 186 | 187 | def format_columns(items, ncols, sep=' '): 188 | items = list(items) 189 | assert items 190 | assert all(len(item) == len(items[0]) for item in items) 191 | nrows = (len(items) + ncols-1) // ncols 192 | items = pad(items, nrows * ncols) 193 | columns = [items[i:i+nrows] for i in range(0, len(items), nrows)] 194 | return map(sep.join, zip(*columns)) 195 | 196 | def pad(items, n): 197 | return items + [' ' * len(items[0])] * (n - len(items)) 198 | 199 | ## for row in format_columns(map(str, range(10)), 3): print row 200 | #. 0 4 8 201 | #. 1 5 9 202 | #. 2 6 203 | #. 3 7 204 | #. 205 | 206 | 207 | if __name__ == '__main__': 208 | import sys 209 | toplevel(sys.argv[1]) 210 | -------------------------------------------------------------------------------- /hal_watch.py: -------------------------------------------------------------------------------- 1 | """ 2 | See step-by-step running of the vm. Hit enter at each step. 3 | """ 4 | 5 | import sys 6 | 7 | import ansi 8 | import hal_vm 9 | 10 | def main(filename, inputs): 11 | run(hal_vm.load(filename, inputs)) 12 | 13 | def run(vm): 14 | while True: 15 | sys.stdout.write(ansi.clear_screen) 16 | vm.show() 17 | sys.stdin.read(1) 18 | try: 19 | vm.step() 20 | except hal_vm.Halt as e: 21 | print(e) 22 | break 23 | 24 | if __name__ == '__main__': 25 | main(sys.argv[1], sys.argv[2]) 26 | -------------------------------------------------------------------------------- /literals.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | """ 4 | 5 | def search(strings, chars): 6 | """Given a sequence of strings and an iterator of chars, return True 7 | if any of the strings would be a prefix of ''.join(chars); but 8 | only consume chars up to the end of the match.""" 9 | raise NotImplementedError 10 | -------------------------------------------------------------------------------- /literals_hal.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | """ 4 | 5 | def compile_pattern(strings): 6 | """Given a sequence of strings, return a HAL 100 assembly-language 7 | program that will report as soon as any of the strings appears in the 8 | machine's input.""" 9 | raise NotImplementedError 10 | 11 | def compile_just_A(): 12 | """Return a HAL 100 program that will report when the letter 'A' 13 | appears in its input. This is just an example of what you might 14 | do for compile_pattern(['A']).""" 15 | program = """ 16 | ;; Execution starts here at address 0. 17 | getch r1 18 | ifne r1,'A',fail 19 | found 20 | fail notfound 21 | """ 22 | return program.splitlines() 23 | 24 | if __name__ == '__main__': 25 | import hal_vm, hal_watch 26 | program = compile_just_A() 27 | sample_input = "An A and a gold star just for you!" 28 | hal_watch.run(hal_vm.load_program(program, sample_input)) 29 | -------------------------------------------------------------------------------- /plus.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | """ 4 | 5 | def search(re, chars): 6 | """Given a regular expression and an iterator of chars, return True if 7 | re matches some prefix of ''.join(chars); but only consume chars 8 | up to the end of the match.""" 9 | raise NotImplementedError 10 | 11 | # Regular-expression constructors; the re above is built by these. 12 | # Feel free to change these definitions if it helps. 13 | def literal(char): return ('literal', char, None) 14 | def chain(re1, re2): return ('chain', re1, re2) 15 | def either(re1, re2): return ('either', re1, re2) 16 | def plus(re): return ('plus', re, None) 17 | -------------------------------------------------------------------------------- /plus_compiled.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | 4 | In a functional, black-box sense, this is no different from star.py, 5 | and the same tests are applied. But you're to compile the regexes 6 | into a representation that will make matching more efficient. 7 | """ 8 | 9 | def search(re, chars): 10 | """Given a regular expression and an iterator of chars, return True if 11 | re matches some prefix of ''.join(chars); but only consume chars 12 | up to the end of the match.""" 13 | raise NotImplementedError 14 | 15 | # Regular-expression constructors; the re above is built by these. 16 | # Feel free to change these definitions if it helps. 17 | def literal(char): return ('literal', char, None) 18 | def chain(re1, re2): return ('chain', re1, re2) 19 | def either(re1, re2): return ('either', re1, re2) 20 | def plus(re): return ('plus', re, None) 21 | -------------------------------------------------------------------------------- /regex_parse.py: -------------------------------------------------------------------------------- 1 | """ 2 | Derived from https://github.com/darius/peglet/blob/master/examples/regex.py 3 | """ 4 | 5 | from functools import reduce 6 | from peglet import Parser, join 7 | 8 | def make_parser(maker): 9 | def empty(): return maker.empty 10 | def literal(char): return maker.literal(char) 11 | def dot(): return maker.anyone 12 | def chain(r, s): return maker.chain(r, s) 13 | def either(r, s): return maker.either(r, s) 14 | def both(r, s): return maker.both(r, s) 15 | 16 | def optional(r): return either(r, empty()) 17 | 18 | if not hasattr(maker, 'star') and not hasattr(maker, 'plus'): 19 | def star(r): raise Exception("No star() or star() constructor supplied") 20 | def plus(r): raise Exception("No plus() or star() constructor supplied") 21 | else: 22 | if hasattr(maker, 'star'): 23 | star = maker.star 24 | else: 25 | def star(r): return optional(plus(r)) 26 | if hasattr(maker, 'plus'): 27 | plus = maker.plus 28 | else: 29 | def plus(r): return chain(r, star(r)) 30 | 31 | if hasattr(maker, 'oneof'): 32 | oneof = maker.oneof 33 | else: 34 | def oneof(chars): return reduce(either, map(literal, chars)) 35 | 36 | parser = Parser(r""" 37 | regex = exp $ 38 | 39 | exp = term [|] exp either 40 | | term & exp both 41 | | term 42 | | empty 43 | 44 | term = factor term chain 45 | | factor 46 | 47 | factor = primary [*] star 48 | | primary [+] plus 49 | | primary [?] optional 50 | | primary 51 | 52 | primary = \( exp \) 53 | | \[ charset \] join oneof 54 | | [.] dot 55 | | \\(.) literal 56 | | ([^.()&*+?|[\]]) literal 57 | 58 | charset = char charset 59 | | 60 | char = \\(.) 61 | | ([^\]]) 62 | """, 63 | join=join, 64 | **locals()) 65 | return lambda s: parser(s)[0] 66 | 67 | class Struct(object): 68 | def __init__(self, **kwargs): 69 | self.__dict__.update(kwargs) 70 | 71 | 72 | # Test 73 | 74 | if globals().get('halp'): 75 | 76 | class Mk: 77 | empty = [''] 78 | 79 | def literal(self, char): 80 | return [char] 81 | 82 | def chain(self, r, s): 83 | return [ri + sj for ri in r for sj in s] 84 | 85 | def either(self, r, s): 86 | return r + s 87 | 88 | parse = make_parser(Mk()) 89 | 90 | ## parse('(Chloe|Yvette), a( precocious)? (toddler|writer)') 91 | #. ['Chloe, a precocious toddler', 'Chloe, a precocious writer', 'Chloe, a toddler', 'Chloe, a writer', 'Yvette, a precocious toddler', 'Yvette, a precocious writer', 'Yvette, a toddler', 'Yvette, a writer'] 92 | -------------------------------------------------------------------------------- /star.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | """ 4 | 5 | def search(re, chars): 6 | """Given a regular expression and an iterator of chars, return True if 7 | re matches some prefix of ''.join(chars); but only consume chars 8 | up to the end of the match.""" 9 | raise NotImplementedError 10 | 11 | # Regular-expression constructors; the re above is built by these. 12 | # Feel free to change these definitions if it helps. 13 | def literal(char): return ('literal', char, None) 14 | def chain(re1, re2): return ('chain', re1, re2) 15 | def either(re1, re2): return ('either', re1, re2) 16 | def plus(re): return ('plus', re, None) 17 | def star(re): return ('star', re, None) 18 | -------------------------------------------------------------------------------- /star_compiled.py: -------------------------------------------------------------------------------- 1 | """ 2 | Fill in this stub. 3 | 4 | In a functional, black-box sense, this is no different from star.py, 5 | and the same tests are applied. But you're to compile the regexes 6 | into a representation that will make matching more efficient. 7 | """ 8 | 9 | def search(re, chars): 10 | """Given a regular expression and an iterator of chars, return True if 11 | re matches some prefix of ''.join(chars); but only consume chars 12 | up to the end of the match.""" 13 | raise NotImplementedError 14 | 15 | # Regular-expression constructors; the re above is built by these. 16 | # Feel free to change these definitions if it helps. 17 | def literal(char): return ('literal', char, None) 18 | def chain(re1, re2): return ('chain', re1, re2) 19 | def either(re1, re2): return ('either', re1, re2) 20 | def plus(re): return ('plus', re, None) 21 | def star(re): return ('star', re, None) 22 | -------------------------------------------------------------------------------- /tests.py: -------------------------------------------------------------------------------- 1 | """ 2 | Tests for the problems. 3 | """ 4 | 5 | import sys 6 | import traceback 7 | 8 | from regex_parse import make_parser 9 | import hal_vm 10 | 11 | all_problems = ('literals finite plus star plus_compiled star_compiled ' 12 | 'literals_hal both').split() 13 | solutions = set(all_problems) 14 | 15 | def main(argv): 16 | problems = argv[1:] or all_problems 17 | for problem in problems: 18 | test_problem(problem) 19 | return 0 20 | 21 | def test_problem(name): 22 | module = __import__(name) 23 | check = globals()['check_'+name] 24 | print("Testing " + name + ".py: ") 25 | try: 26 | check(module) 27 | except NotImplementedError: 28 | print(" Nothing to test yet.") 29 | else: 30 | if name in solutions: 31 | url = "https://github.com/darius/regexercise_solutions/blob/master/%s.py" % name 32 | print(" Passed! See my solution at " + url) 33 | else: 34 | print(" Passed.") 35 | 36 | def check(module, regex_string, string, remainder): 37 | parse = make_parser(module) 38 | check_search(module.search, regex_string, parse(regex_string), 39 | string, remainder) 40 | 41 | def check_search(search, pattern_string, pattern, string, remainder): 42 | correct_result = remainder is not None 43 | stream = iter(string) 44 | try: 45 | result = search(pattern, stream) 46 | except NotImplementedError: 47 | raise 48 | except: 49 | print_bounded_traceback() 50 | print(show_test_case(pattern_string, pattern, string, remainder, False)) 51 | sys.exit(1) 52 | unconsumed = ''.join(stream) 53 | test_case = show_test_case(pattern_string, pattern, string, remainder, 54 | True, result, unconsumed) 55 | if remainder is None: 56 | assert result is False, "Wrong result." + test_case 57 | assert not unconsumed, "The stream should be exhausted." + test_case 58 | else: 59 | assert result is True, "Wrong result." + test_case 60 | assert unconsumed == remainder, "Too much or too litle of the stream was consumed." + test_case 61 | 62 | def show_test_case(pattern_string, pattern, string, remainder, 63 | completed, result=None, unconsumed=None): 64 | correct_result = remainder is not None 65 | pairs = () 66 | if pattern_string is not None: 67 | pairs += (("Regex:", pattern_string),) 68 | pairs += (("Pattern: ", pattern), ("Input:", string)) 69 | if not completed: 70 | pairs += (("Result should be:", correct_result),) 71 | elif result is not correct_result: 72 | pairs += (("Result should be:", correct_result), 73 | ("But result is: ", result)) 74 | if not completed: 75 | pairs += (("Remainder should be:", remainder),) 76 | elif unconsumed != (remainder or ''): 77 | pairs += (("Remainder should be:", remainder), 78 | ("But remainder is: ", unconsumed)) 79 | return ''.join('\n %s %r' % pair for pair in pairs) 80 | 81 | def print_bounded_traceback(): 82 | lines = traceback.format_exc().splitlines() 83 | if 30 < len(lines): 84 | lines = lines[:15] + [' [...]'] + lines[-15:] 85 | print('\n'.join(lines)) 86 | 87 | def check_literals(module): 88 | check_search(module.search, None, [], '', None) 89 | check_search(module.search, None, [], 'wheee', None) 90 | check_search(module.search, None, [''], 'wheee', 'wheee') 91 | check1_base(LiteralsRegexMaker(module.search)) 92 | return "Literal patterns: all tests passed." 93 | 94 | def check_literals_hal(module): 95 | # TODO other check_literals tests -- move 'em into regex tests 96 | check1_base(LiteralsRegexMaker(HalSearch(module.compile_pattern))) 97 | return "Literal patterns for HAL: all tests passed." 98 | 99 | def HalSearch(compiler): 100 | def search(regex, chars): 101 | program = compiler(regex) 102 | return not not hal_vm.load_program(program, chars).run() 103 | # XXX make stream track getch 104 | return search 105 | 106 | class LiteralsRegexMaker: 107 | def __init__(self, search): 108 | self.search = search 109 | empty = [''] 110 | def literal(self, char): return [char] 111 | def chain(self, r, s): return [ri + sj for ri in r for sj in s] 112 | def either(self, r, s): return r + s 113 | 114 | def check1_base(module): 115 | check(module, r'X', '', None) 116 | check(module, r'X', 'wheee', None) 117 | check(module, r'X', 'X', '') 118 | check(module, r'X', 'XXXee', 'XXee') 119 | check(module, r'X', 'yX', None) 120 | check(module, r'X|X', 'yX', None) 121 | check(module, r'X|YY', 'YX', None) 122 | check(module, r'X|X', 'Xy', 'y') 123 | check(module, r'X|YY', 'XYY', 'YY') 124 | check(module, r'allo|a', 'alloha', 'lloha') 125 | check(module, r'ab', 'aab', None) 126 | check(module, r'ab', 'aba', 'a') 127 | check(module, r'rat|cat', 'cats are fat', 's are fat') 128 | check(module, r'XXX', 'XX', None) 129 | check(module, r'XXXY', 'XXXish?', None) 130 | check(module, r'XXXY', 'XXXY?', '?') 131 | check(module, r'bababy', 'bababyish', 'ish') 132 | check(module, r'bababy', 'babababyish', None) 133 | 134 | def check_finite(module): 135 | check1_base(module) 136 | check(module, r'(0|1)'*20, 137 | '01100011000110001100 how are you?', 138 | ' how are you?') 139 | check(module, r'(0|1)'*20, 140 | '0110001100011000110 how are you?', 141 | None) 142 | check(module, r'(aa|a)'*2, 143 | 'aaa b', 144 | 'a b') 145 | check(module, r'(aa|a)'*40, 146 | 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b', 147 | 'aaaaa b') 148 | check(module, r'(aa|a)'*40, 149 | 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b', 150 | None) 151 | return "Abstract data: all tests passed." 152 | 153 | def check_plus(module): 154 | check_finite(module) 155 | check(module, r'A+', 'A', '') 156 | check(module, r'A+', 'AAA+, would do again.', 'AA+, would do again.') 157 | check(module, r'a[bc]+d', 'abdomen', 'omen') 158 | check(module, r'a[bc]+d', 'abcbdcb', 'cb') 159 | check(module, r'a[bc]+d', 'addomen', None) 160 | check(module, r'(cat|dog)+like', 'dogcatcatdogcatdogdogcatdogcatcatdogcatdogdogcatlikely', 'ly') 161 | return "Plus: all tests passed." 162 | 163 | def check_plus_compiled(module): 164 | check_plus(module) 165 | return "Plus_compiled: all tests passed." 166 | 167 | def check_star(module): 168 | check_plus(module) 169 | check(module, r'a*', '', '') 170 | check(module, r'ba*', '', None) 171 | check(module, r'ba*', 'bc', 'c') 172 | check(module, r'ab*c', 'abcd', 'd') 173 | check(module, r'ab*c', 'abd', None) 174 | check(module, r'yo(ab|c*a)*ba', 'yoaabcaccaabbaba', 'ba') 175 | # These tests go beyond the official interface, but can help: 176 | # check(module, r'()*', '', '') 177 | # check(module, r'(()())*', '', '') 178 | check(module, r'a(b*)*d', 'ad attacks', ' attacks') 179 | check(module, r'a(b*)*d', 'abdomen', 'omen') 180 | return "Star: all tests passed." 181 | 182 | def check_star_compiled(module): 183 | check_star(module) 184 | return "Star_compiled: all tests passed." 185 | 186 | def check_both(module): 187 | check_star(module) 188 | check(module, r'a&b', 'a', None) 189 | check(module, r'a&a', 'a', '') 190 | check(module, r'a*(a*&[ab][ab][ab])b', 'aaaabb', 'b') 191 | check(module, r'a*(a*&[ab][ab][ab])b', 'aabbbb', None) 192 | check(module, r'(c[aeiou])*&[caeiou][caeiou][caeiou][caeiou]', 193 | 'cacophony', 'phony') 194 | check(module, r'(c[aeiou])*&[caeiou][caeiou][caeiou][caeiou]', 195 | 'caccphony', None) 196 | # XXX lots more tests needed 197 | return "Both: all tests passed." 198 | 199 | if __name__ == '__main__': 200 | import sys 201 | sys.exit(main(sys.argv)) 202 | --------------------------------------------------------------------------------