Perl Programming - Bslides

8/8/2019 Perl Programming - Bslides

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Perl for Linguists

Michael Hammond

University of Arizona

Perl for Linguists p.1/3


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Perl for linguists



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Perl for linguists Why programming?



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Perl for linguists Why programming? Why Perl?



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Learn a little Perl.



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Learn a little Perl. More advanced Perl. . .



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Why programming?



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Why programming? Collect data



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Analyze data



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Analyze data Model theory



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Analyze data Model theory

General professional skills



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Code for this tutorialAll the code for this presentation is available over

the web at the following URL:

http://linguistics.arizona.edu/~hammond/berkeley.html

http://linguistics.arizona.edu/~hammond/berkeley.htmlhttp://linguistics.arizona.edu/~hammond/berkeley.html


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Unzipping the programs1. Download the file programfiles.zip by

right-clicking on the link, selecting save targetas, and selecting your desktop as thedestination.

2. Unzip the file by double-clicking on thedownloaded file on your desktop and movingall the files there to a new directory on the

desktop.

3. Open the MS-DOS prompt in the newdirectory by double-clicking on the filedoswindow.bat.



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Collecting data



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Collecting data Running experiments locally (expprog.pl)



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Running experiments locally with a GUI(tkexp.pl)



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Running experiments remotely(Bailey & Hahn replication, bhrep.cgi)

http://linguistics.arizona.edu/cgi-bin/bhrep.cgihttp://linguistics.arizona.edu/cgi-bin/bhrep.cgi


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Assembling corpora from local static

resources (makecorpus.pl)



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Assembling corpora from local static

resources (makecorpus.pl) Assembling corpora from nonlocal dynamic

resources: the web (websearch.pl)



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Analyzing data



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Analyzing data Looking for patterns (visgrep.pl)



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Counting things (neightk.pl)



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Counting things (neightk.pl) Finding verbs (verbs.pl)



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Modeling theory



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Modeling theory

Optimality Theory (web interface,

sylpars.pl)

http://wacky.ccit.arizona.edu/~ling/mhspf.htmlhttp://wacky.ccit.arizona.edu/~ling/mhspf.html


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Modeling theory

Optimality Theory (web interface,

sylpars.pl) N-gram models (a bunch of examples from a

course on Statistical NLP that I did recently)

http://wacky.ccit.arizona.edu/~ling/mhspf.htmlhttp://linguistics.arizona.edu/~hammond/ling696f-sp03/http://linguistics.arizona.edu/~hammond/ling696f-sp03/http://wacky.ccit.arizona.edu/~ling/mhspf.html


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General programming skills



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General programming skills

Web programming



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Why Perl?



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Why Perl?

Free



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Why Perl?

! Free!

Multi-platform



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Why Perl?

" Free"

Multi-platform" Easy



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Why Perl?

# Free#

Multi-platform# Easy#

Multiple dialects



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Why Perl?

$ Free$

Multi-platform$ Easy$

Multiple dialects$ Powerful regular expression tools



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Why Perl?

% Free%

Multi-platform% Easy%

Multiple dialects% Powerful regular expression tools% Written by a linguist

http://www.acm.org/crossroads/xrds1-2/lwall.htmlhttp://www.acm.org/crossroads/xrds1-2/lwall.html


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Why Perl?

& Free&

Multi-platform& Easy&

Multiple dialects& Powerful regular expression tools& Written by a linguist& Perl poetry

http://www.acm.org/crossroads/xrds1-2/lwall.htmlhttp://www.programming-x.com/programming/perl-poetry.htmlhttp://www.programming-x.com/programming/perl-poetry.htmlhttp://www.acm.org/crossroads/xrds1-2/lwall.html


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Why Perl?

' Free'

Multi-platform' Easy'

Multiple dialects' Powerful regular expression tools' Written by a linguist' Perl poetry' Obfuscated perl, japhs, etc.

http://www.acm.org/crossroads/xrds1-2/lwall.htmlhttp://www.programming-x.com/programming/perl-poetry.htmlhttp://www.cpan.org/misc/japhhttp://www.cpan.org/misc/japhhttp://www.programming-x.com/programming/perl-poetry.htmlhttp://www.acm.org/crossroads/xrds1-2/lwall.html


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Learn a little perl. . .



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( Windows basics



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) Windows basics)

Perl syntax



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0 Windows basics0

Perl syntax0 IO



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1 Windows basics1

Perl syntax1 IO1

Regular expressions



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2 Windows basics2

Perl syntax2 IO2

Regular expressions2 Where to find out more



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Windows basics



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Windows basics3 It is easiest to invoke perl programs from the

DOS prompt. (If configured properly, you canjust double-click them though.)



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DOS prompt. (If configured properly, you canjust double-click them though.)4

perl myprogram.pl: invokes the perl

interpreter with a program myprogram.pl.



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DOS prompt. (If configured properly, you canjust double-click them though.)5

perl myprogram.pl: invokes the perl

interpreter with a program myprogram.pl.5

ctrl-c: stops the current program



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A goal

6 We will build our efforts around an example

program: a program that parses a text file inEnglish into sentences and then tries to findall the verbs (verbs.pl).

6

This exemplifies simple data and controlstructures and what we might callcomputational linguistic reasoning.

6

We wont get to the full version of thisprogramits infinitely expandableactuallybut we can get a good start.


P i i


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Programming overview


P i i


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7 Implement some idea as perl code (write theprogram).


P i i


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8 Convert code into something the computercan execute (run perl on your code).


P i i


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9 Convert code into something the computercan execute (run perl on your code).

9

Program execution (run perl on your code).


P i i


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@ Implement some idea as perl code (write theprogram).

@ Convert code into something the computercan execute (run perl on your code).

@

Program execution (run perl on your code).@ Results (what happens as a consequence).


P l t


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Perl syntax


Perl syntax


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Perl syntax

A A perl program is a series of statements.


Perl syntax


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Perl syntax

B A perl program is a series of statements.B

Statements can be organized into groups.


Perl syntax


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Perl syntax

C A perl program is a series of statements.C

Statements can be organized into groups.C Statements are operations on some bit of

data, e.g. print this string, add these

numbers, etc.


Perl syntax


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Perl syntax

D A perl program is a series of statements.D

Statements can be organized into groups.D Statements are operations on some bit of

data, e.g. print this string, add these

numbers, etc.D Groups of statements can apply:

1. only when specific conditions hold, or2. more than once, etc.


St t t


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Statements


St t t


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Statements

E A statement includes some operation(typically marked with following parentheses),ends with a semicolon, and may containmore. For example:


Statements


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Statements

F A statement includes some operation(typically marked with following parentheses),ends with a semicolon, and may containmore. For example:

F

print("Hello!"); (prints the stringHello!)


Statements


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Statements

G A statement includes some operation(typically marked with following parentheses),ends with a semicolon, and may containmore. For example:

G

print("Hello!"); (prints the stringHello!)G

rand(5); (gets a random number between 0

and 5)


Statements


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Statements

H A statement includes some operation(typically marked with following parentheses),ends with a semicolon, and may containmore. For example:

H

print("Hello!"); (prints the stringHello!)H

rand(5); (gets a random number between 0

and 5)H

localtime(); (gets the current time)


Try it


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Try it


Try it


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Try it

1. Open the DOS window (through the startmenu or by clicking on the doswindow.baticon.)


Try it


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Try it


2. Type edit myprogram.pl


Try it


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Try it



3. Type print("I am a linguist!");


Try it


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y t




4. Select Save and then Exit from the Filemenu.


Try it


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y




4. Select Save and then Exit from the Filemenu.

5. Type perl myprogram.pl at the prompt.


Variables


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Variables


Variables


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Variables

I Notice how rand() and localtime() dontseem to do anything.


Variables


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Variables

P Notice how rand() and localtime() dontseem to do anything.

P What they do is return a string. You can savethat result and then print it:


Variables


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Variables

Q Notice how rand() and localtime() dontseem to do anything.

Q What they do is return a string. You can savethat result and then print it:

$myvariable = localtime();

print($myvariable);


Variables


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Va ab es


Variables


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R Simple scalar variables: $myvar,$aVariable, $x.


Variables


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S Simple scalar variables: $myvar,$aVariable, $x.

S A value is assigned to a variable with theassignment operator =.


Variables


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T Simple scalar variables: $myvar,$aVariable, $x.

T A value is assigned to a variable with theassignment operator =.

T

Variables can hold numbers, strings, etc.


Reading a file


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Reading a file


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U First use open() to open a file and associateit with a handle, e.g.open(F, "myfile.txt");.


Reading a file


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V First use open() to open a file and associateit with a handle, e.g.open(F, "myfile.txt");.

V Read a line from the file with record-reading

operator:

W

F

X

.


Reading a file


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Y First use open() to open a file and associateit with a handle, e.g.open(F, "myfile.txt");.

Y Read a line from the file with record-reading

operator:

F

a

.Y When youre done, close the handle:

close(F);.


Sample code


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open(F,"myfile.txt");

$line = ;

print($line);close(F);


Control structures


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b

if: conditional applicationb

while: iteration as long as some condition istrueb

for: iteration for a specific number of timesb

foreach: iteration for every member of a list


More sample code


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while ($line = ) {

print($line);}

close(F);


Arrays


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Arrays


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c Array variables: a list of variables groupedtogether: @myarray, @thisBigArray,@them.


Arrays


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d Array variables: a list of variables groupedtogether: @myarray, @thisBigArray,

@them.d Adding an element to the end of an array:

push(@myarray, "hat");.


Arrays


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e Array variables: a list of variables groupedtogether: @myarray, @thisBigArray,

@them.e Adding an element to the end of an array:

push(@myarray, "hat");.e Retrieving an element from the end of an

array: $it = pop(@myarray);.


Arrays


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f Array variables: a list of variables groupedtogether: @myarray, @thisBigArray,

@them.f Adding an element to the end of an array:

push(@myarray, "hat");.f Retrieving an element from the end of an

array: $it = pop(@myarray);.f

Retrieving a specific element:print($myarray[4]); (array indices startat 0).


Sample code again


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while ($line = ) {

push(@mylines, $line);}

close(F);

foreach $theline (@mylines) {print($theline);

}


Regular expressions


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Regular expressions


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g Regular expression: a restrictive way ofindicating string patterns.


Regular expressions


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h Regular expression: a restrictive way ofindicating string patterns.

h

$myvar =~ /regexp/: does $myvarcontain the regular expression?


Regular expressions


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i Regular expression: a restrictive way ofindicating string patterns.

i

$myvar =~ /regexp/: does $myvarcontain the regular expression?

i

$myvar =~ s/regexp/string/: if$myvar contains the regular expression,replace it with the string.


The verb-finding program


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p Recall that the program breaks an Englishtext file into sentences and does its best at

finding all the verbs.




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q Recall that the program breaks an Englishtext file into sentences and does its best at

finding all the verbs.q An hour is not enough time to figure out how

to do all of this, but just the bits weve coveredare a lot of it (verbs.pl).


Where to find out more


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r The free ActiveState Perl were using comeswith extensive web-based documentation.




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s The free ActiveState Perl were using comeswith extensive web-based documentation.

s In any perl implementation the perldoccommand can be used to find out lots andlots of stuff.




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t The free ActiveState Perl were using comeswith extensive web-based documentation.

t In any perl implementation the perldoccommand can be used to find out lots andlots of stuff.

t The official and best perl website iswww.cpan.org, but see also www.perl.org.


Advanced stuff
http://www.cpan.org/http://www.perl.org/http://www.perl.org/http://www.cpan.org/


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Advanced stuff


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u Lets now do some more advanced stuff.


Advanced stuff


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v Lets now do some more advanced stuff.v Advanced in terms of perl.


Advanced stuff


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w Lets now do some more advanced stuff.w Advanced in terms of perl.w Advanced in terms of linguistics.


Advanced perl


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Advanced perl

Obj i d i d bli l


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x Object-oriented programming and public perlmodules


Advanced perl

Obj t i t d i d bli l


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y Object-oriented programming and public perlmodules

y

Tk (editperl.pl, visgrep.pl)


Advanced perl

Obj t i t d i d bli l


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Object-oriented programming and public perlmodules

Tk (editperl.pl, visgrep.pl) Remote computing (bhexp.cgi, dbiex.pl,

websearch.pl)


Object-oriented programming


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Object oriented (OO) programming is another


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Object-oriented (OO) programming is anotherstyle of programming.





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OO Programs are a network of things orobjects, not a list of commands.





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Objects have their own data and specializedfunctions for dealing with their own data.





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Objects have their own data and specializedfunctions for dealing with their own data. Objects can be refer to other objects or inherit

the properties of other objects.


Translating to OO


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Translating to OO

Original verb-finding program: verbs pl


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Original verb finding program: verbs.pl.


Translating to OO

Original verb-finding program: verbs pl


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Original verb finding program: verbs.pl. OO verb-finding program: verbsOO.pl.


Caveats


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Caveats

OO programs are longer.


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Caveats



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OO programs are longer. OO programs are slower.


Caveats



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OO p og a s a e o ge OO programs are slower. OO programming in perl is not orthodox OO

(lots of oddments).


Caveats



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p g g OO programs are slower. OO programming in perl is not orthodox OO

(lots of oddments).

00 programming isnt intuitive for most folks.


Caveats



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p g g OO programs are slower. OO programming in perl is not orthodox OO

(lots of oddments).

00 programming isnt intuitive for most folks. Unfortunately, 00 programming is essential for

some modules.


Tk


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Tk

Tk is an independent language for making


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p g g ggraphical user interfaces.


Tk



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graphical user interfaces.

There is a special perl module so that youcan build GUIs indirectly using Tk.


Tk



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This module is widely available for Unix/Linuxand Windows, but not clear if its available forMacs.


Tk



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This module is widely available for Unix/Linuxand Windows, but not clear if its available forMacs.

If you want to write programs in Perl thatreally look like modern computer programs,then you need to use Tk.


GUI coding


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GUI coding

Tk programs use OO programming style;b i d ll bj


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buttons, windows, etc. are all objects.


GUI coding

Tk programs use OO programming style;b tt i d t ll bj t


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You create these objects and then yourprogram waits for the user to interact withthem.


GUI coding

Tk programs use OO programming style;b tt i d t ll bj t


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You create these objects and then yourprogram waits for the user to interact withthem.

makecorpus.pl makecorpusTk.pl


Remote computing


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Remote computing

CGI (Common Gateway Interface):programs that run remotely (generating


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programs that run remotely (generating

javascript and HTML: bhexp.cgi)


Remote computing



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javascript and HTML: bhexp.cgi) Interacting with local or remote databases

(generating sql: dbiex.pl)


Remote computing



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javascript and HTML: bhexp.cgi) Interacting with local or remote databases

(generating sql: dbiex.pl) Interacting with the web generally

(websearch.pl)


Modeling


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Modeling

Perl not good for computational clarity; notwell-defined


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well-defined


Modeling



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well-defined

Perl exceptionally good at string processing


Modeling



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well defined

Perl exceptionally good at string processing Computational tasks as string processing:

sylpars.pl


What now?


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What now?

Programming and perl hopefullydemystified. . .


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demystified. . .


What now?

j Programming and perl hopefullydemystified. . .


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demystified. . .j

Some ideas about what you can do with it ifyoure thinking that you need to program.


What now?

k Programming and perl hopefullydemystified. . .


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de yst edk

Some ideas about what you can do with it ifyoure thinking that you need to program.

k

If you already know some perl, perhaps someother ideas about what to do with what youalready know.


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Perl Programming - Bslides