From 3b390967e7c2ee4ac6d1a67c77f40ed43005e012 Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Sun, 20 Nov 2016 11:27:07 +0100
Subject: Initial

---
 ast.cpp | 244 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 244 insertions(+)
 create mode 100644 ast.cpp

(limited to 'ast.cpp')

diff --git a/ast.cpp b/ast.cpp
new file mode 100644
index 0000000..88d716a
--- /dev/null
+++ b/ast.cpp
@@ -0,0 +1,244 @@
+#include <stdexcept>
+#include <cctype>
+#include "ast.h"
+
+using namespace std;
+
+
+ParseError::ParseError(const string &what_arg)
+	:runtime_error(what_arg){}
+ParseError::ParseError(const char *what_arg)
+	:runtime_error(what_arg){}
+
+
+Lambda::Lambda(){}
+Lambda::Lambda(const Name &arg,const AST &ast)
+	:arg(arg),body(ast){}
+
+
+AST::AST()
+	:type(Type::tuple){}
+
+AST AST::makeNumber(Number numval){
+	AST ast; ast.type=AST::Type::number; ast.numval=numval; return ast;
+}
+AST AST::makeString(String strval){
+	AST ast; ast.type=AST::Type::string; ast.strval=strval; return ast;
+}
+AST AST::makeName(Name nameval){
+	AST ast; ast.type=AST::Type::name; ast.nameval=nameval; return ast;
+}
+AST AST::makeIndex(Index indexval){
+	AST ast; ast.type=AST::Type::index; ast.indexval=indexval; return ast;
+}
+AST AST::makeTuple(Terms terms){
+	AST ast; ast.type=AST::Type::tuple; ast.terms=terms; return ast;
+}
+AST AST::makeLambda(Lambda lambdaval){
+	AST ast; ast.type=AST::Type::lambda; ast.lambdaval=lambdaval; return ast;
+}
+AST AST::makeLambda(const Name &arg,const AST &body){
+	AST ast; ast.type=AST::Type::lambda; ast.lambdaval.arg=arg; ast.lambdaval.body=body; return ast;
+}
+AST AST::makeNative(const Native &native){
+	AST ast; ast.type=AST::Type::native; ast.nativeval=native; return ast;
+}
+
+
+bool iswordchar(char c){
+	return isalpha(c)||isdigit(c)||strchr("!$%&*+,-./:;<=>?@^_|~",c)!=nullptr;
+}
+
+class AST::Tokeniser{
+	const string source;
+	const i64 size;
+	i64 index=0,nextat=0;
+
+public:
+	Tokeniser(const string &source)
+			:source(source),size(source.size()){
+		// cerr<<"Tokeniser: initialised with <<"<<source<<">>"<<endl;
+		advance();
+	}
+
+	bool eof() const {
+		return index==-1;
+	}
+
+	string get(){
+		if(index==-1)throw logic_error("Tokeniser::get() after last token");
+		if(nextat==index)throw logic_error("Tokeniser::get() before advance()");
+		// cerr<<"Tokeniser: got <<"<<source.substr(index,nextat-index)<<">>"<<endl;
+		// cerr<<"           left: <<"<<source.substr(nextat)<<">>"<<endl;
+		return source.substr(index,nextat-index);
+	}
+
+	bool advance(){
+		index=nextat;
+		// cerr<<"advance: reading from <<"<<source.substr(index)<<">>"<<endl;
+
+		do {
+			while(index<size&&isspace(source[index])){
+				index++;
+			}
+			if(index==size){
+				index=nextat=-1;
+				return false;
+			}
+			if(source[index]!='#')break;
+			while(index<size&&source[index]!='\n'){
+				index++;
+			}
+			if(index==size){
+				index=nextat=-1;
+				return false;
+			}
+		} while(isspace(source[index])||source[index]=='#');
+
+		if(strchr("'()\\",source[index])!=nullptr){
+			nextat=index+1;
+			return true;
+		} else if(index<size-1&&source[index]=="λ"[0]&&source[index+1]=="λ"[1]){
+			nextat=index+2;
+			return true;
+		} else if(isdigit(source[index])||(index<size-1&&source[index]=='-'&&isdigit(source[index+1]))){
+			nextat=index+1;
+			while(nextat<size&&isdigit(source[nextat])){
+				nextat++;
+			}
+			return true;
+		} else if(iswordchar(source[index])){
+			nextat=index+1;
+			while(nextat<size&&iswordchar(source[nextat])){
+				nextat++;
+			}
+			return true;
+		} else {
+			throw ParseError(string("Invalid token starting with '")+source[index]+"'");
+		}
+	}
+};
+
+AST& AST::parse(AST::Tokeniser &tokeniser){
+	if(tokeniser.eof()){
+		throw ParseError("No tokens to parse");
+	}
+	const string &token=tokeniser.get();
+	if(token.size()==0){
+		throw logic_error("Unexpected empty token from tokeniser");
+	}
+	if(isdigit(token[0])||(token.size()>1&&token[0]=='-'&&isdigit(token[1]))){
+		// cerr<<"AST::parse: type = number"<<endl;
+		type=Type::number;
+		numval=strtol(token.data(),NULL,10);
+	} else if(iswordchar(token[0])){
+		// cerr<<"AST::parse: type = name"<<endl;
+		type=Type::name;
+		nameval=token;
+	} else if(token=="("){
+		// cerr<<"AST::parse: type = tuple"<<endl;
+		type=Type::tuple;
+		while(true){
+			if(!tokeniser.advance()){
+				throw ParseError("List opened with '(' not closed");
+			}
+			if(tokeniser.get()==")")break;
+			terms.push_back(AST().parse(tokeniser));
+		}
+	} else if(token=="'"){
+		if(!tokeniser.advance()){
+			throw ParseError("Unexpected EOF after quote");
+		}
+		parse(tokeniser);
+		quoted=true;
+	} else if(token=="\\"||token=="λ"){
+		type=Type::lambda;
+		if(!tokeniser.advance()){
+			throw ParseError("Unexpected EOF after '\\'");
+		}
+		const string &arg=tokeniser.get();
+		if(!iswordchar(arg[0])){
+			throw ParseError("Name expected after '\\'");
+		}
+		lambdaval.arg=arg;
+		if(!tokeniser.advance()){
+			throw ParseError("Body expected after argument of '\\'");
+		}
+		lambdaval.body=AST().parse(tokeniser);
+	} else if(token==")"){
+		throw ParseError("Unexpected token '"+token+"'");
+	} else {
+		throw logic_error("Unrecognised token from tokeniser: '"+token+"'");
+	}
+	return *this;
+}
+
+AST::AST(const string &source)
+	:AST(source.data()){};
+
+AST::AST(const char *source){
+	Tokeniser tokeniser(source);
+	parse(tokeniser);
+	if(tokeniser.advance()){
+		throw ParseError("Trailing content in source");
+	}
+}
+
+
+ostream& operator<<(ostream &os,const AST &ast){
+	if(ast.quoted){
+		os<<"'";
+	}
+
+	switch(ast.type){
+		case AST::Type::number:
+			os<<ast.numval;
+			break;
+
+		case AST::Type::string:
+			os<<'"';
+			for(char c : ast.strval){
+				switch(c){
+					case 9: os<<"\\t"; break;
+					case 10: os<<"\\n"; break;
+					case 13: os<<"\\r"; break;
+					default:
+						if(c>=32&&c<=126){
+							os<<c;
+						} else {
+							os<<"\\x"
+							  <<"0123456789abcdef"[(unsigned char)c/16]
+							  <<"0123456789abcdef"[(unsigned char)c%16];
+						}
+				}
+			}
+			os<<'"';
+			break;
+
+		case AST::Type::name:
+			os<<ast.nameval;
+			break;
+
+		case AST::Type::index:
+			os<<'['<<ast.indexval<<']';
+			break;
+
+		case AST::Type::tuple:
+			os<<'(';
+			for(i64 i=0;i<(i64)ast.terms.size();i++){
+				if(i!=0)os<<' ';
+				os<<ast.terms[i];
+			}
+			os<<')';
+			break;
+
+		case AST::Type::lambda:
+			os<<"\\"<<ast.lambdaval.arg<<' '<<*ast.lambdaval.body;
+			break;
+
+		case AST::Type::native:
+			os<<"\\ [native]";
+			break;
+	}
+	return os;
+}
-- 
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