Trends in Programming Language Design Professor Alfred V. Aho Department of Computer Science Overview Columbia University – The most influential languages Trends in – Trends in language design Programming Language Design – Design issues in the AWK programming language
16 October 2002
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The Most Influential Programming The Most Influential Programming Languages of All Time Languages of All Time
• Assembler • Fortran – 1950s – 1950s – Step up from machine language – Created by a team led by John Backus of IBM – Available on virtually every machine – Initial focus: scientific computing – Influenced FI, FII, FIV, F77, F90, HPF, F95
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The Most Influential Programming The Most Influential Programming Languages of All Time Languages of All Time
• Cobol • Lisp – 1950s – 1950s – Created by U.S. DOD – Created by John McCarthy – Grace Murray Hopper influential in initial – Initial focus: symbol processing development – Influenced Scheme, Common Lisp, MacLisp, – Initial focus: business data processing Interlisp – Influenced C68, C74, C85, PL/1 – Dominant language for programming AI applications – The world’s most popular programming language for many years until the early 1990s
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• Algol 60 • Basic – 1960 – Early 1960s – Algol 60 Report introduced BNF as a notation for – Created by John Kemeny and Thomaz Kurtz of describing the syntax of a language Dartmouth – Initial focus: general purpose programming – Initial focus: a simple, easy-to-use imperative – First block-structured language language – Influenced Algol 68, Pascal, Modula, Modula 2, – Influenced dozens of dialects, most notably Visual Oberon, Modula 3 Basic, probably the world’s most popular – Revised Algol 60 Report: P. Naur, J. Backus, F. programming language today Bauer, J. Green, C. Katz, J. McCarthy, A. Perlis, H. Rutishauer, K. Samelson, B. Vauquois, J. Wegstein, A. van Wijngaarden, M. Woodger
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The Most Influential Programming The Most Influential Programming Languages of All Time Languages of All Time
• Simula 67 • C – 1967 – 1970s – Created by Ole-Johan Dahl, Bjorn Myhrhaug and – C was created by Dennis Ritchie at Bell Labs initially Kristen Nygaard at the Norwegian Computing as a systems programming language for Centre, Olso implementing UNIX – Algol 60 with classes and coroutines – C++ was created by Bjarne Stroustrup at Bell Labs in – First object-oriented programming language the 1980s adding object orientation to C – Designed for discrete-event simulation – Influenced ANSI C, Java – Influenced C++, Smalltalk, Java – C/C++ has become the world’s most widely used systems programming language
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The Most Influential Programming The Most Influential Programming Languages of All Time Languages of All Time
• ML • Scripting Languages – 1970s – Typeless languages for “glue programming” – Created by Robin Milner at University of Edinburgh – awk – Initial focus: meta-language for program verification – perl – One of the most widely used functional – sh programming languages – tkl – Influenced Standard ML, Miranda, Haskell – many more
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• Simplicity and expressiveness for productivity • ADA • PL/1 • Robustness, safety and security • Architecturally neutral and portable • APL • Postscript • Internet savvy • C# • Prolog • Concurrency • Performance • HTML • SQL • Object orientation • Interoperability • Java • Visicalc
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Overview of Awk Awk Program
From The AWK Programming Language, by Alfred V. • Format of an awk program Aho, Brian W. Kernighan and Peter J. Weinberger, pattern { action } Addison Wesley, 1988 pattern { action } … pattern { aciton } “Awk is a convenient and expressive programming language that can be applied to a wide variety of common computing and data-processing tasks.” • Execution model repeatedly read input line apply patterns for each pattern that matches execute associated action
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Example How much did each person earn during their shift?
Data file Name Hours-worked Hourly-rate Bob 5 10 Stephen 0 8 Name Hours-worked Hourly-rate Susan 10 15 Bob 5 10 Bob 6.5 11 Stephen 0 8 Susan 10 15 Command line Bob 6.5 11 awk ‘$2 > 0 { print $1, $2 * $3 }’ data
Awk output Bob 50 Susan 150 Bob 71.5
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Name Hours-worked Hourly-rate Name Hours-worked Hourly-rate Bob 5 10 Bob 5 10 Stephen 0 8 Stephen 0 8 Susan 10 15 Susan 10 15 Bob 6.5 11 Bob 6.5 11 Awk program { wages[$1] += $2 * $3 } Awk program END { for (emp in wages) $1 ~ /Bob/ { hw += $2 } print emp “ earned $” wages[emp] } END { print “Bob worked “ hw “ hours” } Awk output Stephen earned $0 Awk output Bob earned $121.5 Susan earned $150 Bob worked 11.5 hours
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What are everyone’s wages, sorted by Awk Patterns name?
Name Hours-worked Hourly-rate • BEGIN Bob 5 10 • END Stephen 0 8 Susan 10 15 • Expression Bob 6.5 11 • Regular expression Awk program • Compound pattern { wages[$1] += $2 * $3 } END { for (emp in wages) • Range pattern print emp “ earned $” wages[emp] | “sort” } Awk output Bob earned $121.5 Stephen earned $0 Susan earned $150
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Awk Actions Some useful awk “one-liners”
• expressions • Print the total number of input lines •print/printf END { print NR } •if ( expression ) statement • Print every line longer than 80 characters length($0) > 80 •if ( expression ) statement else statement • Print the last field of every input line •while ( expression ) statement { print $NF } •for( expression ; expression ; expression ) statement • Print the first two fields, in opposite order, of every line •for( variable in array ) statement { print $2, $1 } •do statement while ( expression ) • Print in reverse order the fields of every line •break/continue/next/exit/exit expression { for ( i = NF; i > 0; i = i-1 ) printf(“%s “, $I) •{ statements } printf(“\n”) }
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