rs_read() can parse symbols.

Mostly, anyway. R5RS says that '...' is a valid identifier. ReScheme doesn't support it yet, but will when I get around to adding macros. Next up is the symbol table (probably a ternary search tree), and then, hopefully, garbage collection.
ingramj · Aug 9, 2011 · 866a19a · 866a19a
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diff --git a/README b/README
@@ -13,32 +13,30 @@ Compilation and Usage
 "CC = gcc", or whatever is appropriate. There are no external dependencies.
 
 So far, ReScheme is just a pretty-printer, and doesn't evaluate expressions.
-Integers, characters, booleans, and null have been implemented.
+Integers, characters, booleans, null, and symbols have been implemented.
 
     $ make
     $ ./rescheme
     > 123
     123
-    > -9876
-    -9876
-    > +45
-    45
     > #b1011
     11
-    > #o0644
-    420
     > #x-14bead
     -1359533
     > #\a
     #\a
-    > #\B
-    #\B
     > #\newline
     #\newline
     > #T
     #t
     > ()
     ()
+    > asdf-123
+    asdf-123
+    > <=>
+    <=>
+    > ReScheme
+    rescheme
     > <Ctrl-D>
     $
 

diff --git a/read.c b/read.c
@@ -12,7 +12,8 @@
 
 
 enum state { ST_START, ST_DECIMAL, ST_HASH, ST_BINARY, ST_OCTAL, ST_HEX,
-             ST_CHARACTER, ST_CHAR_N, ST_CHAR_S, ST_CHAR_T, ST_END };
+             ST_CHARACTER, ST_CHAR_N, ST_CHAR_S, ST_CHAR_T, ST_SYMBOL,
+             ST_END };
 
 
 /* Turn the string in buf into an rs_fixnum, or die trying. */
@@ -36,19 +37,36 @@ static void get_word(struct rs_buf *buf, FILE *in, int c, int n);
 #define BIN_DIGIT '0': case '1'
 
 #define OCT_DIGIT \
-	'0': case '1': case '2': case '3': \
-	case '4': case '5': case '6': case '7'
+	BIN_DIGIT: case '2': case '3': case '4': case '5': case '6': case '7'
 
 #define DIGIT \
-	'0': case '1': case '2': case '3': case '4': \
-	case '5': case '6': case '7': case '8': case '9'
+	OCT_DIGIT: case '8': case '9'
 
 #define HEX_DIGIT \
-	'0': case '1': case '2': case '3': case '4': \
-	case '5': case '6': case '7': case '8': case '9': \
-	case 'a': case 'A': case 'b': case 'B': case 'c': case 'C': \
+	DIGIT: case 'a': case 'A': case 'b': case 'B': case 'c': case 'C': \
 	case 'd': case 'D': case 'e': case 'E': case 'f': case 'F'
 
+#define LC_LETTER \
+	'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g': \
+	case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n': \
+	case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u': \
+	case 'v': case 'w': case 'x': case 'y': case 'z'
+
+#define UC_LETTER \
+	'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G': \
+	case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N': \
+	case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U': \
+	case 'V': case 'W': case 'X': case 'Y': case 'Z'
+
+#define SYMBOL_INIT \
+	LC_LETTER: case UC_LETTER: case '!': case '$': case '%': case '*': \
+	case '/': case ':': case '<': case '=': case '>': case '?': case '^': \
+	case '_': case '~'
+
+#define SYMBOL_SUB \
+	SYMBOL_INIT: case DIGIT: case '+': case '-': case '.': case '@'
+
+
 #define PUSH_BACK(c, in) \
 	if (c != EOF && ungetc(c, in) == EOF) \
 		rs_fatal("ungetc failed:");
@@ -93,15 +111,20 @@ rs_object rs_read(FILE *in)
 				break;
 			case '+': case '-':
 				BUF_PUSH(&buf, c);
-				/* Look ahead to see if it's followed by a digit. */
+				/* Look ahead to see if it's a number or a symbol. */
 				c = getc(in);
 				switch (c) {
 				case DIGIT:
 					BUF_PUSH(&buf, c);
 					cur_state = ST_DECIMAL;
 					break;
+				case DELIM:
+					PUSH_BACK(c, in);
+					obj = rs_symbol_create(rs_buf_str(&buf));
+					cur_state = ST_END;
+					break;
 				default:
-					rs_fatal("expected a digit");
+					rs_fatal("expected a digit or a delimiter");
 				}
 				break;
 			case '#':
@@ -116,6 +139,10 @@ rs_object rs_read(FILE *in)
 					rs_fatal("non-empty lists have not been implemented");
 				}
 				break;
+			case SYMBOL_INIT:
+				BUF_PUSH(&buf, tolower(c));
+				cur_state = ST_SYMBOL;
+				break;
 			default:
 				rs_fatal("invalid expression");
 			}
@@ -308,6 +335,21 @@ rs_object rs_read(FILE *in)
 			cur_state = ST_END;
 			break;
 
+		case ST_SYMBOL:
+			switch (c) {
+			case SYMBOL_SUB:
+				BUF_PUSH(&buf, tolower(c));
+				break;
+			case DELIM:
+				PUSH_BACK(c, in);
+				obj = rs_symbol_create(rs_buf_str(&buf));
+				cur_state = ST_END;
+				break;
+			default:
+				rs_fatal("'%c' cannot appear in an identifier", c);
+			}
+			break;
+
 		default:
 			rs_fatal("got into an impossible state");
 		}