Second

1 files changed, 94 insertions, 0 deletions

diff --git a/parser.c b/parser.c
new file mode 100644
index 0000000..7e7a1c2
--- /dev/null
+++ b/parser.c
@@ -0,0 +1,94 @@
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "parser.h"
+#include "util.h"
+
+typedef struct Cursor{
+	const char *s;
+	int l;
+} Cursor;
+
+typedef enum Tokentype{
+	TT_EOF, //str=NULL, len=-1
+	TT_SYMBOL,
+	TT_WORD,
+	TT_NUMBER,
+
+	TT_ERR=-1 //str is an error description, len=-1
+} Tokentype;
+
+typedef struct Token{
+	Tokentype type;
+	const char *str; //pointer into source
+	int len;
+} Token;
+
+#define SYMBOLCHARS "()[]"
+
+
+static Token tt_make(Tokentype type,const char *str,int len){
+	Token tok={type,str,len};
+	return tok;
+}
+
+static Token tt_eof(void){
+	return tt_make(TT_EOF,NULL,-1);
+}
+
+static Token tt_err(const char *errstr){
+	return tt_make(TT_ERR,errstr,-1);
+}
+
+
+static void advance(Cursor *cursor,int n){
+	assert(cursor->l>=n);
+	cursor->s+=n;
+	cursor->l-=n;
+}
+
+static bool iswordchar(char c){
+	return strchr(SYMBOLCHARS,c)==NULL&&c>=33&&c<=126;
+}
+
+static Token nexttoken(Cursor *cursor){
+	while(cursor->l>=1&&isspace(*cursor->s))advance(cursor,1);
+	if(cursor->l==0)return tt_eof();
+
+	if(strchr(SYMBOLCHARS,*cursor->s)!=NULL){
+		advance(cursor,1);
+		return tt_make(TT_SYMBOL,cursor->s-1,1);
+	}
+
+	if(isdigit(*cursor->s)||(cursor->l>=2&&cursor->s[0]=='-'&&isdigit(cursor->s[1]))){
+		char *endp;
+		strtod(cursor->s,&endp);
+		assert(endp>cursor->s);
+		int len=endp-cursor->s;
+		advance(cursor,len);
+		return tt_make(TT_NUMBER,cursor->s-len,len);
+	}
+
+	int i;
+	for(i=0;i<cursor->l;i++){
+		if(!iswordchar(cursor->s[i]))break;
+	}
+	if(i==0){
+		return tt_err("Unrecognised character while looking for next token");
+	}
+	advance(cursor,i);
+	return tt_make(TT_WORD,cursor->s-i,i);
+}
+
+
+static ParseRet parse_(Cursor *cursor){
+	;
+}
+
+
+ParseRet parse(const char *source,int length){
+	Cursor cursor={source,length};
+	return parse_(&cursor);
+}