Assignment 1 – 4 Solution

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Assignment 1:

Write a flex program even.l which takes a sequence of integers as its input and outputs a count of the number of even integers a \n and no other characters. Note put return 0; at end of the main function as codemark regards non zero exit status as an error.

Assignment 2:

Write a flex program comments.l which removes comments from a slightly odd programming language and sends the remaining code to its output.

  • ** means regard the two asterisks and all following characters on that line as comment.

  • anything between { and } is comment, potentially across multiple lines.

  • a { inside a comment is just part of the comment.

  • a { not followed by } is regarded as a syntax error and your program should output the phrase “syntax error\n” in place of the the remaining input and exit when it detects this.

  • a } not preceded by a matching { is regarded as a syntax error and your program should output the phrase “syntax error\n” and exit at this place.

  • between double-quote characters {} and ** are regarded as part of a string and dont indicate comments.

  • there’s no facility to put a double-quote inside a string.

  • Note put return 0; at end of the main function as codemark regards non zero exit status as an error.

Assignment 3:

Write a flex program that reads a whitespace (space tab or newline) seperated list of Irish car registration numbers and outputs the number of years since registration followed by a new line for each one.

If an invalid registration is detected the program should output the word “INVALID” followed by a newline character.

The current specification for number plates is the format YYY-CC-SSSSSS. Those issued from 1987 to 2012 had the format YY-CC-SSSSSS.

The components are: YYY – a 3-digit year (e.g. 131 for January to June 2013; 132 for July to December 2013) YY from 1987-2012 – a 2-digit year (e.g. 87 for 1987; 05 for 2005) CC – a 1- or 2-character County/City identifier (e.g. L for Limerick City and County; SO for County Sligo). SSSSSS – a 1- to 6-digit sequence number, starting with the first vehicle registered in the county/city that year/period.

2014-present C Cork CE Clare CN Cavan CW Carlow D Dublin DL Donegal G Galway KE Kildare KK Kilkenny KY Kerry L Limerick LD Longford LH Louth LM Leitrim LS Laois MH Meath MN Monaghan MO Mayo OY Offaly RN Roscommon SO Sligo T Tipperary W Waterford WH Westmeath WX Wexford WW Wicklow Differences 1987-2013 L Limerick City LK County Limerick

TN North Tipperary TS South Tipperary T INVALID

W Waterford City WD County Waterford

Note you can define sub-parts of regular expressions in the definitions section and then use these in the rule: NUMBER [0-9]… COUNTY KK|… YEAR [0-9]… %% {YEAR}{COUNTY}{NUMBER} { do stuff… }

Assignment 4:

Write a Bison program that takes a series of uppercase Roman numerals as input, parses them, and takes semantic actions to compute and print the corresponding Hindu-Arabic numeral.

Test cases will be newline seperated lists of Roman numerals and the program should output the corresponding Hindu-Arabic numeral followed by a new line for each one.

If an invalid number is detected the program should output the words “syntax error” followed by a newline character to standard output and then exit.

Your source code should be in two files, roman.l and roman.y, and the defaults filenames lex.yy.c should be generated. Put the two files roman.l and roman.y only into a zip archive and use the codemark submit archive page to upload. Do not use subdirectories. Supported archive file formats include Zip, Tar-GZip, Tar-BZip2, RAR, 7-zip, LhA, StuffIt and other old and obscure formats.

The Roman numeral system for representing numbers was developed around 500 b.c.

As the Romans conquered much of the world that was known to them, their numeral system spread throughout Europe, where Roman numerals remained the primary manner for representing numbers for centuries. Around a.d. 1300, Roman numerals were replaced throughout most of Europe with the more effective Hindu-Arabic system still used today.

Roman numerals, as used today, are based on seven symbols Symbol I V X L C D M Value 1 5 10 50 100 500 1,000

The original pattern for Roman numerals used the symbols I, V, and X (1, 5, and 10) as simple tally marks. Each marker for 1 (I) added a unit value up to 5 (V), and was then added to (V) to make the numbers from 6 to 9:

        I, II, III, IIII, V, VI, VII, VIII, VIIII, X.

The numerals for 4 (IIII) and 9 (VIIII) proved problematic (among other things, they are easily confused with III and VIII), and are generally replaced with IV (one less than 5) and IX (one less than 10). This feature of Roman numerals is called subtractive notation.

The numbers from 1 to 10 (including subtractive notation for 4 and 9) are expressed in Roman numerals as follows:

        I, II, III, IV, V, VI, VII, VIII, IX, X.

The system being basically decimal, tens and hundreds follow the same pattern:

Thus 10 to 100 (counting in tens, with X taking the place of I, L taking the place of V and C taking the place of X):

        X, XX, XXX, XL, L, LX, LXX, LXXX, XC, C.

Note that 40 (XL) and 90 (XC) follow the same subtractive pattern as 4 and 9.

Similarly, 100 to 1000 (counting in hundreds):

        C, CC, CCC, CD, D, DC, DCC, DCCC, CM, M.

Again – 400 (CD) and 900 (CM) follow the standard subtractive pattern.