Curry: Example Programs
Here is a collection of (small) Curry programs.
References to larger applications can be found
here.
Usually, each program contains
some example goals at the end in order to see its
intended application.
The programs are sorted by the main language features they use
so that people interested in the various features of Curry
can look at these examples:
- rev.curry:
list concatenation and naive reverse
- higher.curry:
some standard higher-order functions: map and foldr
- quicksort.curry:
functional quicksort based on filtering the smaller and larger elements
- qsortlet.curry:
quicksort based on splitting the unsorted list into a pair of lists
with smaller and larger elements
- inflists.curry:
functions defined on infinite lists, like fib and primes
- escher_higher.curry:
implementation of module "Higher" from the Escher report
- nats.curry:
a basic example: natural numbers are represented as S-terms
and the substraction between numbers is defined by reversing
the addition
- family_fun.curry:
a database for family relationships (functional logic style)
- family_nd.curry:
a database for family relationships (functional logic style
with non-deterministic functions)
- horseman.curry:
a puzzle from equational logic programming (solving questions like
"How many men and horses have 8 heads and 20 feet?")
- first.curry:
lazy functional logic programming with infinite lists
- last.curry:
compute the last element of a list using a flexible append function
(i.e., inverting list concatenation)
- member.curry:
list membership defined by a single conditional rule based on
a flexible append function (i.e., inverting list concatenation)
- mergesort.curry:
merge sort: sorting two lists by merging the sorted first
and second half of the list
- assembler.curry:
a one-pass assembler:
translation of a sequence of arbitrary jump-instructions into machine code
where logical variables are used to resolve forward jump addresses
- nondetfunc.curry:
some "classical" examples for non-deterministic functions
like non-deterministic list insertion, permutation,
and permutation sort
- family_nd.curry:
a database for family relationships (functional logic style
with non-deterministic functions)
- colormap_nd.curry:
graph coloring with non-deterministic functions
exploiting the demand-driven search due to lazy evaluation in Curry
- colormap.curry:
map coloring with test-and-generate
(corresponds to logic programming with delays)
- digit.curry:
small example for the use of arithmetic functions acting
as passive constraints
- rigidadd.curry:
small example from the POPL'97 paper for the evaluation
with residuation: the addition of natural numbers acts as
a passive constraint waiting for the instantiation of is arguments
- see also all examples for passive constraints
- infresiduate.curry:
an example for a potential disadvantage of residuation [Hanus JLP'95]:
with residuation, the program has an infinite search space
but with narrowing, the search space is finite
- account.curry:
concurrent object-oriented programming: a bank account implemented
as an active object ("account server")
- iodemo.curry:
some demos of the monadic I/O concept
- diamond.curry:
printing a regular diamond of numbers on the standard output
(an adaptation from the Prolog programming contest at JICSLP'98 in Manchester)
- arithseq.curry:
some simple examples for the arithmetic sequence notation
- multgen.curry:
a few examples for list comprehensions with multiple generators
- psort.curry:
an implementation of permutation sort using list comprehensions
- default.lcurry:
an implementation of Haskell-like default rules with list comprehensions
- allsols.curry:
a few examples for the use of the library "AllSolutions"
- search.curry:
a simple example for encapsulated search
- prolog.curry:
a simulation of the Prolog top-level shell with different search strategies
- best.curry:
a simple example for the best solution search strategy
- england.curry:
a relational database with encapsulated search examples
- sportsdb.curry:
module SportsDB from the Escher report
showing the implementation of Escher's "forall" construct
by encapsulated search
- ModConc.curry:
a module defining list concatenation several times to be important
by the example modules below
- UseConc1.curry:
a module importing module
ModConc
- UseConc2.curry:
a module importing module
ModConc qualified
in order to avoid name conflicts
Here are a few examples that are implementations of
programs from John Lloyd's papers on Escher.
- escher_perm.curry:
module "Permute" from new Escher report
(computation of permutations with a concatentation and a split
function)
- escher_higher.curry:
implementation of module "Higher" from the Escher report
- escher_cond.curry:
module "Conditional" from the Escher report
(check membership in a list)
- relational.curry:
module "Relational" from the Escher report
(computing with relations)
- sportsdb.curry:
module SportsDB from the Escher report
showing the implementation of Escher's "forall" construct
by encapsulated search
- england.curry:
a geographical database and some queries from the Escher report
Important note: The programs in this section
work only with implementations
of Curry that support real arithmetic and finite domain constraints,
see, for instance,
PAKCS.
- mortgage.curry:
a classical example for constraint logic programming over
reals: define a mortgage relationship between the principal,
the life of the loan in months, the interest rate, the monthly
repayment, and the outstanding balance. Due to the constraint
programming features, one can solve various problems with
this simple definition.
- circuit.curry:
a further classical example for constraint logic programming over
reals: analysis of electrical circuits
- queens.curry:
a classical example for constraint logic programming over
finite domains: solving the n-queens problem
- smm.curry:
a further classical example for constraint logic programming over
finite domains: solving the "send+more=money" puzzle
- sudoku.curry:
solving Su Doku puzzles in Curry with finite domain constraints.
This examples shows the use of higher-order functions to set up
a set of constraints in a compact way.
- magicseries.curry:
an example for constraint logic programming over
finite domains where lazy evaluation is exploited:
the computation of magic series
Important note: Most of the programs in this section
work only with implementations
of Curry that support distributed programming with port constraints
as described in the
PPDP'99 paper.
- accountport.curry:
the same program as
account.curry
(a bank account implemented as a concurrent object)
but with the use of port constraints
- counter.curry:
a simple counter which can be incremented and queried
from any machine connected to the Internet
- nameserver.curry:
a name server storing an association between names and numbers
which can be queried in a simple manner
from any machine connected to the Internet
- talk.curry:
a simple program implementing the kernel of the Unix "talk"
to enable a conversation between two partners on different machines
connected to the Internet
- sema.curry:
an implementation of semaphores in Curry
- philo.curry:
an implementation of "dining philosophers" problem
using semaphores implemented via ports
- httpget.curry:
a simple example showing the connection to Unix sockets
(not implemented with ports but with more low level Socket library)
- addserver.curry:
an example showing the implementation of a simple client/server application
(the server provides a service to add two numbers).
The implementation does not use ports but the more low level Socket library.
- addnamedserver.curry:
an example showing the implementation of a simple client/server application
(the server provides a service to add two numbers).
The implementation does Unix sockets with symbolic names
based on the library NamedSocket.
- addtimeoutserver.curry:
an example showing the implementation of a simple client/server application
(the server provides a service to add two numbers).
The implementation uses the Socket library and shows the use of
time limits for socket connections on the server side.
Important note: The programs in this section
work only with the libraries of the PAKCS environment for meta-programming
(see library directory pakcs/lib/meta of the current
PAKCS distribution).
- Imports.curry:
Example for using the library
CurryStringClassifier:
extracts the names of all imported modules from a Curry source file.
- putModuleHead.curry:
Example for using the library
CurryStringClassifier:
adds a standard module header to a Curry source file if it is not already there.
Important note: The programs in this section
work only with the library GUI which is available for
the PAKCS environment. A description
of the ideas behind this library can be found in the
PADL'00 paper.
Most of the programs have a function "main" to start the GUI.
- hello.curry:
a simple "Hello world" GUI
- counter.curry:
a simple counter GUI
- temperature.curry:
a converter from Celsius to Fahrenheit and Kelvin where the Celsius
value of the temperature in Celsius is fixed by a slider
- calc.curry:
a desk calculator showing the combination of GUIs with
local state where the state is stored in an object
- checkbutton.curry:
a simple demo for the use of checkbuttons
- config.curry:
a simple demo to show the dynamic reconfiguration of
widget parameters
- events.curry:
a simple demo to show the handling of different events
(e.g., left and right mouse buttons) inside one widget.
- inputmask.curry:
a demo (simple address database) to show widgets in a tabular
orientation by exploiting the
Matrix
construct for widget composition
- hilbert.curry:
drawing a Hilbert curve in a canvas widget
- sierpinski.curry:
drawing a Sierpinski curve in a canvas widget
- fractal.curry:
drawing a fractal curve in a canvas widget
- mail.curry:
a simple mail widget to write and send an email
- menu.curry:
a simple counter GUI to demonstrate the use of menu buttons
- radiotraffic.curry:
a simple demo for the use of radiobuttons: traffic light controller
ensures exclusion in traffic lights.
- scrollbar.curry:
a simple demo for the use of scrollbars
- textappend.curry:
a simple GUI demonstrating the use of
appendValue
in TextEdit widgets
- textstyledappend.curry:
a simple GUI demonstrating the use of
appendStyledValue
in TextEdit widgets (where text can be shown with
colors and font styles)
- counter_controlled.curry:
a simple counter GUI which can be controlled not only by the user
but also by external processes that send messages to the GUI
Important note: The programs in this section
work only with the GUI library Tk which is available for
the PAKCS environment. This library will no longer be supported
in the future since a similar but improved library GUI
(see examples) is available.
A description of the ideas behind this library can be found in the
PADL'00 paper.
Most of the programs have a function "main" to start the
GUI.
- hello.curry:
a simple "Hello world" GUI
- counter.curry:
a simple counter GUI
- temperature.curry:
a converter from Celsius to Fahrenheit and Kelvin where the Celsius
value of the temperature in Celsius is fixed by a slider
- calc.curry:
a desk calculator showing the combination of GUIs with
local state where the state is stored in an object
- checkbutton.curry:
a simple demo for the use of checkbuttons
- config.curry:
a simple demo to show the dynamic reconfiguration of
widget parameters
- inputmask.curry:
a demo (simple address database) to show widgets in a tabular
orientation by exploiting the TkMatrix construct for widget composition
- hilbert.curry:
drawing a Hilbert curve in a canvas widget
- sierpinski.curry:
drawing a Sierpinski curve in a canvas widget
- fractal.curry:
drawing a fractal curve in a canvas widget
- mail.curry:
a simple mail widget to write and send an email
- mailsearch.curry:
the same as the previous mail GUI but with a "search"
button to search an email address by querying an address server
- menu.curry:
a simple counter GUI to demonstrate the use of menu buttons
- radiotraffic.curry:
a simple demo for the use of radiobuttons: traffic light controller
ensures exclusion in traffic lights.
- scrollbar.curry:
a simple demo for the use of scrollbars
- counter_controlled.curry:
a simple counter GUI which can be controlled not only by the user
but also by external processes that send messages to the GUI
Here are simple examples for the use of the functional logic parser
combinators which are defined in the parser library
Parser and are adapted from the paper
"A Functional Logic Perspective of Parsing"
by R. Caballero and F.J. Lopez-Fraguas
(Proc. FLOPS'99, Springer LNCS 1722, pp. 85-99, 1999).
- expr_parser.curry:
a parser for arithmetic expressions over natural numbers
- palindrome.curry:
a parser for palindromes over the alphabet 'a' and 'b'
showing also the possibility to generate correct sentences
with functional logic parsers
- chords.curry:
this program is able to generate appropriate chords for the accompaniment
of a given melody. There is also a
paper which sketches the implementation and describes
the advantages of Curry to implement this application.
- daVinciTest.curry:
some examples to show the use of the library DaVinci
for the visualization of graphs
Back to Homepage of Curry
Michael Hanus