StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<p>A symbol table is just a versioned map of id's to values. This is one solution, using a push and pop of scopes as the versioning mechanism -- push a scope on entry of a scope defining rule and pop on exit.</p> <pre><code>package net.certiv.metal.symbol; import java.util.ArrayList; import java.util.LinkedHashMap; import java.util.Map; import net.certiv.metal.types.ScopeType; import net.certiv.metal.util.Strings; public class Scope { public final int genId; public ScopeType type; public Scope enclosingScope; protected Map<String, Symbol> symbolMap = new LinkedHashMap<String, Symbol>(); public Scope(ScopeType type, final int genId, Scope enclosingScope) { this.type = type; this.genId = genId; this.enclosingScope = enclosingScope; } /** * Define a new variable in the current scope * This is the entry point for adding new variables */ public void define(String name, ArrayList<String> parameters) { String params = Strings.asString(parameters, true, "."); Symbol symbol = new Symbol(null, name + params, null); define(symbol); } /** Define a symbol in the current scope */ private void define(Symbol symbol) { symbol.setScope(this); symbolMap.put(symbol.name, symbol); } /** * Look up the symbol name in this scope and, if not found, * progressively search the enclosing scopes. * Return null if not found in any applicable scope. */ private Symbol resolve(String name) { Symbol symbol = symbolMap.get(name); if (symbol != null) return symbol; if (enclosingScope != null) return enclosingScope.resolve(name); return null; // not found } /** * Lookup a variable starting in the current scope. * This is the entry point for lookups */ public Symbol resolve(String name, ArrayList<String> parameters) { String params = Strings.asString(parameters, true, "."); return resolve(name + params); } /** Where to look next for symbols */ public Scope enclosingScope() { return enclosingScope; } public String toString() { return symbolMap.keySet().toString(); } } package net.certiv.metal.types; public enum ScopeType { GLOBAL, LOCAL; } package net.certiv.metal.symbol; import net.certiv.metal.converter.BaseDescriptor; import net.certiv.metal.types.ValueType; public class Symbol { protected Scope scope; // the owning scope protected BaseDescriptor descriptor; protected String name; protected ValueType type; public Symbol(BaseDescriptor descriptor, String name, ValueType type) { this.descriptor = descriptor; this.name = name; this.type = type; } public BaseDescriptor getDescriptor() { return descriptor; } public String getName() { return name; } public ValueType getType() { return type; } public void setScope(Scope scope) { this.scope = scope; } public Scope getScope() { return scope; } public int genId() { return scope.genId; } public String toString() { if (type != null) return '<' + getName() + ":" + type + '>'; return getName(); } } package net.certiv.metal.symbol; import java.util.ArrayList; import java.util.Stack; import net.certiv.metal.types.ScopeType; import net.certiv.metal.util.Log; public class SymbolTable { protected Stack<Scope> scopeStack; protected ArrayList<Scope> allScopes; protected int genId; public SymbolTable() { init(); } protected void init() { scopeStack = new Stack<>(); allScopes = new ArrayList<>(); genId = 0; Scope globals = new Scope(ScopeType.GLOBAL, nextGenId(), null); scopeStack.push(globals); allScopes.add(globals); } public Scope pushScope() { Scope enclosingScope = scopeStack.peek(); Scope scope = new Scope(ScopeType.LOCAL, nextGenId(), enclosingScope); scopeStack.push(scope); allScopes.add(scope); return scope; } public void popScope() { scopeStack.pop(); } public Scope currentScope() { if (scopeStack.size() > 0) { return scopeStack.peek(); } Log.error(this, "Unbalanced scope stack."); return allScopes.get(0); } public Scope getScope(int genId) { for (Scope scope : scopeStack) { if (scope.genId == genId) return scope; } return null; } private int nextGenId() { genId++; return genId; } public String toString() { StringBuilder sb = new StringBuilder(); for (Scope scope : scopeStack.subList(0, scopeStack.size() - 1)) { sb.append(scope.toString()); } return sb.toString(); } } </code></pre>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload