final-project-sandyzhengg23/project_report.txt at main · UChicago-PL/final-project-sandyzhengg23 · GitHub

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
Sandy Zheng
Functional Programming Final Project
Natural Language Task to Calendar Parser

Project Overview

This project is a Haskell command-line program that parses semi-structured
natural language event descriptions into structured calendar events.
The goal is to let a user enter event descriptions such as “gym tomorrow 7am”
or “every monday team meeting 3pm at Harper Cafe” and automatically extract
event information including title, date, time, location, and recurrence.

After parsing the input, the program exports the events into an .ics
calendar file in iCalendar format so that the events can be imported into
calendar applications.

Code Organization

The code is organized into several modules:

- Main.hs
Handles the overall program flow. It reads event descriptions from the user,
parses them into Event values, prints the parsed results, and writes the
final calendar.ics file.

- Parse.hs
Contains the parsing pipeline. It extracts recurrence, location, date,
and time from the input text, and uses the remaining words as the event title.

- Event.hs
Defines the main Event data type that stores the structured event information.

- DateExpr.hs
Defines date expressions such as Today, Tomorrow, explicit dates, and UnknownDate.

- TimeRange.hs
Defines time representations such as SingleTime, TimeSpan, and UnknownTime.

- Recurrence.hs
Defines recurrence values such as EveryDay, EveryWeekday Monday, and NoRecurrence.

- ICS.hs
Converts parsed Event values into iCalendar text and generates the final .ics file.

How to Run / Interact With the Project
The project is run from the command line using:

cabal run

The program prompts the user to enter events one per line.
A blank line ends input. After that, the program prints the
parsed events and generates a file named calendar.ics.

Example inputs:

Dental appointment tomorrow 8am at Downtown
Project presentation 2026-04-10 11am at Regenstein Library
every monday team meeting 3pm at Harper Cafe
every day workout 7am
Dinner tomorrow 6-7 pm

Functional Programming Aspects
This project uses algebraic data types to represent structured information
such as dates, times, recurrence, and events. The parsing logic is implemented
as a sequence of pure transformation functions that extract specific pieces of
information from the input text. Breaking the parser into smaller specialized
passes made the program easier to organize and extend.

Implemented Features

- Parsing of event titles
- Parsing of locations using “at ...” or “@ ...”
- Parsing of relative dates such as “today” and “tomorrow”
- Parsing of explicit ISO-style dates such as 2026-04-10
- Parsing of single times such as 8am or 7pm
- Parsing of simple time ranges such as 6-7 pm
- Parsing of simple recurrence expressions such as “every day” and “every monday”
- Export of parsed events into an .ics calendar file

Limitations

The parser supports a limited set of semi-structured patterns and
does not support unrestricted natural language. Timezone handling is simplified.
More advanced recurrence patterns, date expressions, and conflict detection
are not fully implemented.

Future Work

Possible future extensions include:
- richer natural language date parsing
- more advanced recurrence rules
- conflict detection between events
- direct integration with calendar APIs
- a more interactive text-based interface