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The Variety of Programming Languages

The Variety of Programming Languages. D Goforth COSC 3127. 1. Grouping Languages by Paradigm. imperative functional logical object.oriented scripting??. Imperative Languages (Procedural). since 1940’s, high level since 1950’s statement-oriented closest to underlying machine model

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The Variety of Programming Languages

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  1. The Variety of Programming Languages D Goforth COSC 3127

  2. 1. Grouping Languages by Paradigm • imperative • functional • logical • object.oriented • scripting??

  3. Imperative Languages (Procedural) • since 1940’s, high level since 1950’s • statement-oriented • closest to underlying machine model • e.g. Fortran, COBOL, Algol, Pascal, c

  4. ALGOL 60 example: (see p. 60, Sebesta) (part of program, read in array and find sum) comment input integers into array and find sum; begin integer array intlist[1:99]; integer listlen, counter, sum; sum = 0; readint(listlen); if (listlen>0) ^ (listlen < 100) then begin comment loop to read values; for counter := 1 step 1 until listlen do begin readint(intlist[counter]); sum := sum + intlist[counter] end; printint(sum) end end

  5. Functional Languages (Applicative) • since 1950’s • based on mathematical concept of function • data storage is a ‘side-effect’! • Command-line interpreter model • e.g. LISP, APL, Maple, unix, DOS • BASIC is an imperative/functional hybrid

  6. LISP example: (in a pseudo-lisp dialect) (function to add all numbers in a list ‘lis’; lis may not be a list, or, when it is a list, may contain items others than numbers that can be added ? (define (sumnum lis) (if ((not (list? lis)) ( 0 )) ((number? (firstOf lis)) (plus (firstOf lis)(sumnum (restOf lis)))) ( true (sumnum (restOf lis))))) sumnum ? (sumnum ‘( 4 w (u n 66) 5 3)) 12

  7. Logic Languages • since 1970’s • based on logical implication expressions (=>) • programs determine what combinations of data make expressions true • e.g. Prolog

  8. Prolog example: (program to find the greatest common divisor of two integers U, V; result is value of W) gcd(U, 0, U). gcd(U, V, W) :- not(V=0), R is U mod V, gcd(V, R, W). ?- gcd(10, 15, W). W = 5 ?- gcd(20,30,7). no.

  9. Object-oriented Languages • since 1970’s • abstract data types manipulated by messages invoking methods • e.g. Smalltalk, Actor • C++, java are imperative/object-oriented hybrids

  10. Smalltalk example: (see p. 481, Sebesta) (method to replace two arrays of objects with longer arrays; the arrays ‘names’ and ‘codes’ are instance variables) grow | oldNames oldCodes| oldNames <- names. oldCodes <- codes. names <- Array new: names size + 1. codes <- Array new: codes size + 1. names replaceFrom: 1 to: oldNames size with: oldNames codes replaceFrom: 1 to: oldCodes size with: oldCodes

  11. Scripting Languages • since 1950’s • based on large libraries of routines • e.g. JCL, AWK, Perl

  12. 2. Grouping Languages by Kinship • Sebesta, p. 39 • languages are related to others developed before • many languages mix programming paradigms

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