{"id":12302,"date":"2022-09-30T09:31:14","date_gmt":"2022-09-30T04:01:14","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-how-to-retrieve-tokens-from-a-string-that-are-keywords\/"},"modified":"2022-09-30T09:31:14","modified_gmt":"2022-09-30T04:01:14","slug":"solved-how-to-retrieve-tokens-from-a-string-that-are-keywords","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-how-to-retrieve-tokens-from-a-string-that-are-keywords\/","title":{"rendered":"[Solved] How to retrieve tokens from a string that are keywords?"},"content":{"rendered":"

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Lexing<\/a> is not specific to C (in the sense that you’ll use similar techniques in other programming languages). You could do that with hand-written code (using finite automaton<\/a> coding techniques). You could use a lexer generator like flex<\/a>. You might even use regexprs<\/a>, e.g. regex.h<\/a> functions on POSIX systems.<\/p>\n

Parsing<\/a> is also a well known domain with standard techniques (at least for context free languages<\/a>, if you want some efficiency). You could use recursive descent parsing<\/a>, you could generate a parser using bison<\/a> (which has examples<\/a> very close to your homework) or ANTLR<\/a>. Read more about LL parsing<\/a> & LR parsing<\/a>. BTW, parsing techniques can be used for lexing.<\/p>\n

BTW, there are tons of free software<\/a> (e.g. interpreters of scripting languages like Guile<\/a>, Lua<\/a>, Python<\/a>, etc….), JSON<\/a>, YAML<\/a>, XML… parsers, several compilers (e.g. tinycc<\/a>) etc… illustrating these techniques. You’ll learn a lot by studying their source code.<\/p>\n

It could be easier for your to sometimes have a lookahead of one or two characters, e.g. by first reading the entire line (with getline(3)<\/a> or else fgets(3)<\/a>, and perhaps even readline<\/a>, which gives you a line editor). If you cannot read a whole line consider using fgetc(3)<\/a> and ungetc<\/code> when needed. The classifying utilities from <ctype.h><\/code><\/a> like isalpha<\/a> might be helpful. <\/p>\n

If you care about UTF-8<\/a> (and in principle you should) things become slightly more complex since some Unicode<\/a> characters (like \u20ac, \u00e9, ?, …) are represented in UTF-8 by several bytes. A library like libunistring<\/a> should be very helpful.<\/p>\n<\/p><\/div>\n

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solved How to retrieve tokens from a string that are keywords? <\/p>\n","protected":false},"excerpt":{"rendered":"

[ad_1] Lexing is not specific to C (in the sense that you’ll use similar techniques in other programming languages). You could do that with hand-written code (using finite automaton coding techniques). You could use a lexer generator like flex. You might even use regexprs, e.g. regex.h functions on POSIX systems. Parsing is also a well … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324,712,568,362],"class_list":["post-12302","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-pointers","tag-split","tag-string"],"yoast_head":"\n[Solved] How to retrieve tokens from a string that are keywords? - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-how-to-retrieve-tokens-from-a-string-that-are-keywords\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] How to retrieve tokens from a string that are keywords? - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] Lexing is not specific to C (in the sense that you’ll use similar techniques in other programming languages). You could do that with hand-written code (using finite automaton coding techniques). You could use a lexer generator like flex. You might even use regexprs, e.g. regex.h functions on POSIX systems. Parsing is also a well ... 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