User:Ed Davis: Difference between revisions

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Latest revision as of 03:37, 14 August 2016

Hello, World!

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+Hello, World!
-{{task}}Description of the task
-Lexical Analyzer
-----------------
-From Wikipedia: (https://en.wikipedia.org/wiki/Lexical_analysis)
-Lexical analysis is the process of converting a sequence of characters (such as in a
-computer program or web page) into a sequence of tokens (strings with an identified
-"meaning"). A program that performs lexical analysis may be called a lexer, tokenizer,[1]
-or scanner (though "scanner" is also used to refer to the first stage of a lexer).
-The Task
---------
-Create a lexical analyzer for the Tiny programming language.
-Specification
--------------
-{| class="wikitable"
-|-
-! Characters  !! Regular expression !! Name
-|-
-| integers       || [0-9]+                 || Integer
-|-
-| char literal   || 'x'                    || Integer
-|-
-| identifiers    || [_a-zA-Z][_a-zA-Z0-9]+ || Ident
-|-
-| string literal || ".*"                   || String
-|}
-Notes: For char literals, '\n' is supported as a new line
-character. To represent \, use: '\\'.  \n may also be used in
-Strings, to print a newline. No other special sequences are
-supported.
-operators:
-'*'          multiply                Mul
-'/'          divide                  Div
-'+'          plus                    Add
-'-'          minus and unary minus   Sub and Uminus
-'<'          less than               Lss
-'<='         less than or equal      Leq
-'>'          greater than            Gtr
-'!='         not equal               Neq
-'='          assign                  Assign
-'&&'         and                     And
-symbols:
-'('          left parenthesis        Lparen
-')'          right parenthesis       Rparen
-'{'          left brace              Lbrace
-'}'          right brace             Rbrace
-';'          semi colon              Semi
-','          comma                   Comma
-keywords:
-"if"                                 If
-"while"                              While
-"print"                              Print
-"putc"                               Putc
-comments:    /* ... */   (multi-line)
-Complete list of token types:
-EOI, Print, Putc, If, While, Lbrace, Rbrace, Lparen, Rparen, Uminus, Mul, Div, Add,
-Sub, Lss, Gtr, Leq, Neq, And, Semi, Comma, Assign, Integerk, Stringk, Ident
-Output of the program should be the line and column where the
-found token starts, followed by the Token name.  For tokens
-Integer, Ident and String, the Integer, identifier, or string
-should follow.
-Test Cases
-----------
-/*
-  Hello world
- */
-print("Hello, World!\n");
-Output
-------
-line     4  col     1 Print
-line     4  col     6 Lparen
-line     4  col     7 String   "Hello, World!\n"
-line     4  col    24 Rparen
-line     4  col    25 Semi
-line     5  col     1 EOI
-/*
-  Show Ident and Integers
- */
-phoenix_number = 142857;
-print(phoenix_number, "\n");
-Output
-------
-line     1  col     1 Ident    phoenix_number
-line     1  col    16 Assign
-line     1  col    18 Integer     142857
-line     1  col    24 Semi
-line     2  col     1 Print
-line     2  col     6 Lparen
-line     2  col     7 Ident    phoenix_number
-line     2  col    21 Comma
-line     2  col    23 String   "\n"
-line     2  col    27 Rparen
-line     2  col    28 Semi
-line     3  col     1 EOI
-Diagnostics:
-------------
-The following error conditions should be caught:
-Empty character constant.   Example: ''
-Unknown escape sequence.    Example: '\r'
-Multi-character constant.   Example: 'xx'
-End-of-file in comment.    Closing comment characters not found.
-End-of-file while scanning string literal. Closing string character not found.
-End-of-line while scanning string literal. Closing string character not found before end-of-line.
-Unrecognized character.     Example: |
-Refer additional questions to the C and Python implementations.