https://telosama.xyz/notes/ Recent content in Notes on telosama.xyz Hugo -- gohugo.io en-us © {year} Mon, 13 Mar 2023 16:29:14 +0800 https://telosama.xyz/notes/quiz1/ Mon, 13 Mar 2023 16:29:14 +0800 https://telosama.xyz/notes/quiz1/ Main phases/functions of compiler Lexical Analyzer ==> reads the stream of characters and groups them into meaningful sequences Syntax Analyzer ==> using the components produced by the previous phase, creates a tree like intermediate representation that depicts the grammatical structure of the token stream. Semantic Analyzer ==> using the tree, check the semantic consistency of the source program with the language definition. Also gathers type information Intermediate Code Generator ==> constructs intermediate representation of the target code Machine Independent Code Optimzer ==> Optimizes intermediate representation Code Generator ==> generate target machine code from intermediate representation Machine-dependent Code Optimizer ==> optimizes machine code Compiler Phases Compiler Phases with outputs of each phases: Context Free Grammar (CFG) terminals / tokens ==> elementary symbols of the language nonterminals ==> represent string of terminals productions ==> consists of nonterminal (called left side), an arrow, and sequence of terminals and/or nonterminals (called body) a nonterminal designated as the start symbol Finding FIRST() sets Definitions $\alpha$ ==> string of grammar symbolsl (terminals and/or non-terminals) FIRST($\alpha$) ==> set of terminals that appear as the first symols of one or more strings of terminals generated from $\alpha$ How to compute/find FIRST() sets if $X$ is a terminal, then FIRST($X$) = ${X}$ if $X$ is a nonterminal and $X \to Y_1 Y_2 \cdots Y_k$ is a production, FIRST($X$) = FIRST($Y_1$) If FIRST($Y_i$) contains $\epsilon$ then FIRST($X$) = $\{ FIRST(Y_i) – \epsilon \} \cup \{FIRST(Y_{i+1})\}$, and so on If FIRST($Y_i$) contains $\epsilon$ for all $i$ = 1 to $n$, then add $\epsilon$ to FIRST($X$).