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Chapter 4 Programming in Perl
Chapter 4 Programming in Perl 4.1 More on built-in functions in Perl There are many built-in functions in Perl, and even more are available as modules (see section 4.4) that can be downloaded from various Internet places. Some built-in functions have already been used in chapter 3.1 and some of these and some others will be described in more detail here. 4.1.1 split and join (+ qw, x operator, \here docs", .=) 1 #!/usr/bin/perl 2 3 $sequence = ">|SP:Q62671|RATTUS NORVEGICUS|"; 4 5 @parts = split '\|', $sequence; 6 for ( $i = 0; $i < @parts; $i++ ) { 7 print "Substring $i: $parts[$i]\n"; 8 } • split is used to split a string into an array of substrings. The program above will write out Substring 0: > Substring 1: SP:Q62671 Substring 2: RATTUS NORVEGICUS • The first argument of split specifies a regular expression, while the second is the string to be split. • The string is scanned for occurrences of the regexp which are taken to be the boundaries between the sub-strings. 57 58 CHAPTER 4. PROGRAMMING IN PERL • The parts of the string which are matched with the regexp are not included in the substrings. • Also empty substrings are extracted. Note, however that trailing empty strings are removed by default. • Note that the | character needs to be escaped in the example above, since it is a special character in a regexp. • split returns an array and since an array can be assigned to a list we can write: splitfasta.ply 1 #!/usr/bin/perl 2 3 $sequence=">|SP:Q62671|RATTUS NORVEGICUS|"; 4 5 ($marker, $code, $species) = split '\|', $sequence; 6 ($dummy, $acc) = split ':', $code; 7 print "This FastA sequence comes from the species $species\n"; 8 print "and has accession number $acc.\n"; splitfasta.ply • It is not uncommon that we want to write out long pieces of text using many print statements. -
1. Introduction to Structured Programming 2. Functions
UNIT -3Syllabus: Introduction to structured programming, Functions – basics, user defined functions, inter functions communication, Standard functions, Storage classes- auto, register, static, extern,scope rules, arrays to functions, recursive functions, example C programs. String – Basic concepts, String Input / Output functions, arrays of strings, string handling functions, strings to functions, C programming examples. 1. Introduction to structured programming Software engineering is a discipline that is concerned with the construction of robust and reliable computer programs. Just as civil engineers use tried and tested methods for the construction of buildings, software engineers use accepted methods for analyzing a problem to be solved, a blueprint or plan for the design of the solution and a construction method that minimizes the risk of error. The structured programming approach to program design was based on the following method. i. To solve a large problem, break the problem into several pieces and work on each piece separately. ii. To solve each piece, treat it as a new problem that can itself be broken down into smaller problems; iii. Repeat the process with each new piece until each can be solved directly, without further decomposition. 2. Functions - Basics In programming, a function is a segment that groups code to perform a specific task. A C program has at least one function main().Without main() function, there is technically no C program. Types of C functions There are two types of functions in C programming: 1. Library functions 2. User defined functions 1 Library functions Library functions are the in-built function in C programming system. For example: main() - The execution of every C program starts form this main() function. -
Cygwin User's Guide
Cygwin User’s Guide Cygwin User’s Guide ii Copyright © Cygwin authors Permission is granted to make and distribute verbatim copies of this documentation provided the copyright notice and this per- mission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this documentation under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this documentation into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Free Software Foundation. Cygwin User’s Guide iii Contents 1 Cygwin Overview 1 1.1 What is it? . .1 1.2 Quick Start Guide for those more experienced with Windows . .1 1.3 Quick Start Guide for those more experienced with UNIX . .1 1.4 Are the Cygwin tools free software? . .2 1.5 A brief history of the Cygwin project . .2 1.6 Highlights of Cygwin Functionality . .3 1.6.1 Introduction . .3 1.6.2 Permissions and Security . .3 1.6.3 File Access . .3 1.6.4 Text Mode vs. Binary Mode . .4 1.6.5 ANSI C Library . .4 1.6.6 Process Creation . .5 1.6.6.1 Problems with process creation . .5 1.6.7 Signals . .6 1.6.8 Sockets . .6 1.6.9 Select . .7 1.7 What’s new and what changed in Cygwin . .7 1.7.1 What’s new and what changed in 3.2 . -
Eloquent Javascript © 2011 by Marijn Haverbeke Here, Square Is the Name of the Function
2 FUNCTIONS We have already used several functions in the previous chapter—things such as alert and print—to order the machine to perform a specific operation. In this chap- ter, we will start creating our own functions, making it possible to extend the vocabulary that we have avail- able. In a way, this resembles defining our own words inside a story we are writing to increase our expressive- ness. Although such a thing is considered rather bad style in prose, in programming it is indispensable. The Anatomy of a Function Definition In its most basic form, a function definition looks like this: function square(x) { return x * x; } square(12); ! 144 Eloquent JavaScript © 2011 by Marijn Haverbeke Here, square is the name of the function. x is the name of its (first and only) argument. return x * x; is the body of the function. The keyword function is always used when creating a new function. When it is followed by a variable name, the new function will be stored under this name. After the name comes a list of argument names and finally the body of the function. Unlike those around the body of while loops or if state- ments, the braces around a function body are obligatory. The keyword return, followed by an expression, is used to determine the value the function returns. When control comes across a return statement, it immediately jumps out of the current function and gives the returned value to the code that called the function. A return statement without an expres- sion after it will cause the function to return undefined. -
Automating Your Sync Testing
APPLICATION NOTE By automating system verification and conformance testing to ITU-T synchronization standards, you’ll save on time and resources, and avoid potential test execution errors. This application note describes how you can use the Paragon-X’s Script Recorder to easily record Tcl, PERL and Python commands that can be integrated into your own test scripts for fast and efficient automated testing. AUTOMATING YOUR SYNC TESTING calnexsol.com Easily automate synchronization testing using the Paragon-X Fast and easy automation by Supports the key test languages Pre-prepared G.8262 Conformance recording GUI key presses Tcl, PERL and Python Scripts reduces test execution errors <Tcl> <PERL> <python> If you perform System Verification language you want to record i.e. Tcl, PERL SyncE CONFORMANCE TEST and Conformance Testing to ITU-T or Python, then select Start. synchronization standards on a regular Calnex provides Conformance Test Scripts basis, you’ll know that manual operation to ITU-T G.8262 for SyncE conformance of these tests can be time consuming, testing using the Paragon-X. These tedious and prone to operator error — as test scripts can also be easily tailored well as tying up much needed resources. and edited to meet your exact test Automation is the answer but very often requirements. This provides an easy means a lack of time and resource means it of getting your test automation up and remains on the ‘To do’ list. Now, with running and providing a repeatable means Calnex’s new Script Recorder feature, you of proving performance, primarily for ITU-T can get your automation up and running standards conformance. -
Building Performance Measurement Tools for the MINIX 3 Operating System
Building Performance Measurement Tools for the MINIX 3 Operating System Rogier Meurs August 2006 Contents 1 INTRODUCTION 1 1.1 Measuring Performance 1 1.2 MINIX 3 2 2 STATISTICAL PROFILING 3 2.1 Introduction 3 2.2 In Search of a Timer 3 2.2.1 i8259 Timers 3 2.2.2 CMOS Real-Time Clock 3 2.3 High-level Description 4 2.4 Work Done in User-Space 5 2.4.1 The SPROFILE System Call 5 2.5 Work Done in Kernel-Space 5 2.5.1 The SPROF Kernel Call 5 2.5.2 Profiling using the CMOS Timer Interrupt 6 2.6 Work Done at the Application Level 7 2.6.1 Control Tool: profile 7 2.6.2 Analyzing Tool: sprofalyze.pl 7 2.7 What Can and What Cannot be Profiled 8 2.8 Profiling Results 8 2.8.1 High Scoring IPC Functions 8 2.8.2 Interrupt Delay 9 2.8.3 Profiling Runs on Simulator and Other CPU Models 12 2.9 Side-effect of Using the CMOS Clock 12 3 CALL PROFILING 13 3.1 Introduction 13 3.1.1 Compiler-supported Call Profiling 13 3.1.2 Call Paths, Call and Cycle Attribution 13 3.2 High-level Description 14 3.3 Work Done in User-Space 15 3.3.1 The CPROFILE System Call 15 3.4 Work Done in Kernel-Space 16 3.4.1 The PROFBUF and CPROF Kernel Calls 16 3.5 Work Done in Libraries 17 3.5.1 Profiling Using Library Functions 17 3.5.2 The Procentry Library Function 17 3.5.3 The Procexit Library Function 20 3.5.4 The Call Path String 22 3.5.5 Testing Overhead Elimination 23 3.6 Profiling Kernel-Space/User-Space Processes 24 3.6.1 Differences in Announcing and Table Sizes 24 3.6.2 Kernel-Space Issue: Reentrancy 26 3.6.3 Kernel-Space Issue: The Call Path 26 3.7 Work Done at the Application -
Control Flow, Functions
UNIT III CONTROL FLOW, FUNCTIONS 9 Conditionals: Boolean values and operators, conditional (if), alternative (if-else), chained conditional (if-elif-else); Iteration: state, while, for, break, continue, pass; Fruitful functions: return values, parameters, local and global scope, function composition, recursion; Strings: string slices, immutability, string functions and methods, string module; Lists as arrays. Illustrative programs: square root, gcd, exponentiation, sum an array of numbers, linear search, binary search. UNIT 3 Conditionals: Boolean values: Boolean values are the two constant objects False and True. They are used to represent truth values (although other values can also be considered false or true). In numeric contexts (for example when used as the argument to an arithmetic operator), they behave like the integers 0 and 1, respectively. A string in Python can be tested for truth value. The return type will be in Boolean value (True or False) To see what the return value (True or False) will be, simply print it out. str="Hello World" print str.isalnum() #False #check if all char are numbers print str.isalpha() #False #check if all char in the string are alphabetic print str.isdigit() #False #test if string contains digits print str.istitle() #True #test if string contains title words print str.isupper() #False #test if string contains upper case print str.islower() #False #test if string contains lower case print str.isspace() #False #test if string contains spaces print str.endswith('d') #True #test if string endswith a d print str.startswith('H') #True #test if string startswith H The if statement Conditional statements give us this ability to check the conditions. -
The Return Statement a More Complex Example
We Write Programs to Do Things Anatomy of a Function Definition • Functions are the key doers name parameters Function Call Function Definition def plus(n): Function Header """Returns the number n+1 Docstring • Command to do the function • Defines what function does Specification >>> plus(23) Function def plus(n): Parameter n: number to add to 24 Header return n+1 Function Precondition: n is a number""" Body >>> (indented) x = n+1 Statements to execute when called return x • Parameter: variable that is listed within the parentheses of a method header. The vertical line Use vertical lines when you write Python indicates indentation on exams so we can see indentation • Argument: a value to assign to the method parameter when it is called The return Statement A More Complex Example • Format: return <expression> Function Definition Function Call § Used to evaluate function call (as an expression) def foo(a,b): >>> x = 2 § Also stops executing the function! x ? """Return something >>> foo(3,4) § Any statements after a return are ignored Param a: number • Example: temperature converter function What is in the box? Param b: number""" def to_centigrade(x): x = a A: 2 """Returns: x converted to centigrade""" B: 3 y = b C: 16 return 5*(x-32)/9.0 return x*y+y D: Nothing! E: I do not know Understanding How Functions Work Text (Section 3.10) vs. Class • Function Frame: Representation of function call Textbook This Class • A conceptual model of Python to_centigrade 1 Draw parameters • Number of statement in the as variables function body to execute next to_centigrade x –> 50.0 (named boxes) • Starts with 1 x 50.0 function name instruction counter parameters Definition: Call: to_centigrade(50.0) local variables (later in lecture) def to_centigrade(x): return 5*(x-32)/9.0 1 Example: to_centigrade(50.0) Example: to_centigrade(50.0) 1. -
Subroutines – Get Efficient
Subroutines – get efficient So far: The code we have looked at so far has been sequential: Subroutines – getting efficient with Perl do this; do that; now do something; finish; Problem Bela Tiwari You need something to be done over and over, perhaps slightly [email protected] differently depending on the context Solution Environmental Genomics Thematic Programme Put the code in a subroutine and call the subroutine whenever needed. Data Centre http://envgen.nox.ac.uk Syntax: There are a number of correct ways you can define and use Subroutines – get efficient subroutines. One is: A subroutine is a named block of code that can be executed as many times #!/usr/bin/perl as you wish. some code here; some more here; An artificial example: lalala(); #declare and call the subroutine Instead of: a bit more code here; print “Hello everyone!”; exit(); #explicitly exit the program ############ You could use: sub lalala { #define the subroutine sub hello_sub { print "Hello everyone!\n“; } #subroutine definition code to define what lalala does; #code defining the functionality of lalala more defining lalala; &hello_sub; #call the subroutine return(); #end of subroutine – return to the program } Syntax: Outline review of previous slide: Subroutines – get efficient Syntax: #!/usr/bin/perl Permutations on the theme: lalala(); #call the subroutine Defining the whole subroutine within the script when it is first needed: sub hello_sub {print “Hello everyone\n”;} ########### sub lalala { #define the subroutine The use of an ampersand to call the subroutine: &hello_sub; return(); #end of subroutine – return to the program } Note: There are subtle differences in the syntax allowed and required by Perl depending on how you declare/define/call your subroutines. -
Teach Yourself Perl 5 in 21 Days
Teach Yourself Perl 5 in 21 days David Till Table of Contents: Introduction ● Who Should Read This Book? ● Special Features of This Book ● Programming Examples ● End-of-Day Q& A and Workshop ● Conventions Used in This Book ● What You'll Learn in 21 Days Week 1 Week at a Glance ● Where You're Going Day 1 Getting Started ● What Is Perl? ● How Do I Find Perl? ❍ Where Do I Get Perl? ❍ Other Places to Get Perl ● A Sample Perl Program ● Running a Perl Program ❍ If Something Goes Wrong ● The First Line of Your Perl Program: How Comments Work ❍ Comments ● Line 2: Statements, Tokens, and <STDIN> ❍ Statements and Tokens ❍ Tokens and White Space ❍ What the Tokens Do: Reading from Standard Input ● Line 3: Writing to Standard Output ❍ Function Invocations and Arguments ● Error Messages ● Interpretive Languages Versus Compiled Languages ● Summary ● Q&A ● Workshop ❍ Quiz ❍ Exercises Day 2 Basic Operators and Control Flow ● Storing in Scalar Variables Assignment ❍ The Definition of a Scalar Variable ❍ Scalar Variable Syntax ❍ Assigning a Value to a Scalar Variable ● Performing Arithmetic ❍ Example of Miles-to-Kilometers Conversion ❍ The chop Library Function ● Expressions ❍ Assignments and Expressions ● Other Perl Operators ● Introduction to Conditional Statements ● The if Statement ❍ The Conditional Expression ❍ The Statement Block ❍ Testing for Equality Using == ❍ Other Comparison Operators ● Two-Way Branching Using if and else ● Multi-Way Branching Using elsif ● Writing Loops Using the while Statement ● Nesting Conditional Statements ● Looping Using -
Difference Between Perl and Python Key Difference
Difference Between Perl and Python www.differencebetween.com Key Difference - Perl vs Python A computer program provides instructions for a computer to perform tasks. A set of instructions is known as a computer program. A computer program is developed using a programming language. High-level languages are understandable by programmers but not understandable by the computer. Therefore, those programs are converted to machine-understandable format. Perl and Python are two high-level programming languages. Perl has features such as built-in regular expressions, file scanning and report generation. Python provides support for common programming methodologies such as data structures, algorithms etc. The key difference between Perl and Python is that Perl emphasizes support for common application-oriented tasks while Python emphasizes support for common programming methodologies. What is Perl? Perl is general purpose high-level programing language. It was designed by Larry Wall. Perl stands for Practical Extraction and Reporting Language. It is open source and is useful for text manipulation. Perl runs on various platforms such as Windows, Mac, Linux etc. It is a multi-paradigm language that supports mainly procedural programming and object-oriented programming. Procedure Programming helps to divide the program into functions. Object Oriented programming helps to model a software or a program using objects. Perl is an interpreted language. Therefore, each line is read one after the other by the interpreter. High-level language programs are understandable by the programmer, but they are not understandable by the machine. Therefore, the instructions should be converted into the machine-understandable format. Programming languages such as C and C++ converts the source code to machine language using a compiler. -
Control Flow Statements
Control Flow Statements http://docs.oracle.com/javase/tutorial/java/nutsandbolts/flow.html http://math.hws.edu/javanotes/c3/index.html 1 Control Flow The basic building blocks of programs - variables, expressions, statements, etc. - can be put together to build complex programs with more interesting behavior. CONTROL FLOW STATEMENTS break up the flow of execution by employing decision making, looping, and branching, enabling your program to conditionally execute particular blocks of code. Decision-making statements include the if statements and switch statements. There are also looping statements, as well as branching statements supported by Java. 2 Decision-Making Statements A. if statement if (x > 0) y++; // execute this statement if the expression (x > 0) evaluates to “true” // if it doesn’t evaluate to “true”, this part is just skipped // and the code continues on with the subsequent lines B. if-else statement - - gives another option if the expression by the if part evaluates to “false” if (x > 0) y++; // execute this statement if the expression (x > 0) evaluates to “true” else z++; // if expression doesn’t evaluate to “true”, then this part is executed instead if (testScore >= 90) grade = ‘A’; else if (testScore >= 80) grade = ‘B’; else if (testScore >= 70) grade = ‘C’; else if (testScore >= 60) grade = ‘D’; else grade = ‘F’; C. switch statement - - can be used in place of a big if-then-else statement; works with primitive types byte, short, char, and int; also with Strings, with Java SE7, (enclose the String with double quotes);