Lithp 2 - A Common Lisp-like engine Code

--- a
+++ b/frontend.c
@@ -0,0 +1,114 @@
+/*
+	interactive.c
+
+	an interactive frontend for the lithp2 engine
+
+	(A total rewrite from "lithp" to be more compatible, 
+	and easier to work with.)
+
+	Scott Lawrence
+	2006-Nov-27
+*/
+
+#include <stdio.h>
+#include <string.h> /* for strcmp */
+#include "lithp.h"
+#include "version.h"
+
+#define BUFSIZE (2048)
+
+/* wipe out some useless characters from the input string */
+void trim( char * buf )
+{
+	int pos = 0;
+	if( !buf ) return;
+
+	for( pos=0; buf[pos] != '\0' && pos < BUFSIZE ; pos++ )
+	{
+		switch( buf[pos] ) {
+		
+		/* anything from a 'newline' on gets eliminated */
+		/* this might become obsolete with a better parser later */
+		case( '\n' ):
+		case( '\r' ):
+			buf[pos] = '\0';
+			return;
+			
+		default: 
+			break;
+		}
+	}
+}
+
+/* a simple user input-parsing loop */
+void cmdloop()
+{
+	LITHP_STATE * ls;
+	int done = 0;
+	char buf[BUFSIZE];
+	char *str;
+
+	ls = lithp_create();
+
+	while( !done )
+	{
+		/* print the prompt */
+		printf( "-> " );
+		fflush( stdout );
+
+		/* read in a command */
+		str = fgets( buf, BUFSIZE, stdin );
+		trim( str );
+		if( !str ) {
+			if( feof( stdin )) {
+				/* silently exit on EOF -- ctrl-D */
+				printf( "\n" );
+				done = 1;
+			} else if( ferror( stdin )) {
+				clearerr( stdin );
+				printf( "E: File error %d\n", ferror( stdin ));
+				done = 1;
+			}
+		} else {
+			if( !strcmp( str, "Exit." )) done = 1;
+			if( !done ) {
+				lithp_read( ls, str );
+				lithp_evaluate( ls );
+			}
+		}
+	}
+	lithp_destroy( ls );
+}
+
+
+/* print out a standard usage string */
+void usage( char * argv0 )
+{
+	/*
+	fprintf( stderr, "Usage:  %s [file.lsp]\n", argv0 );
+	fprintf( stderr, "\tSpecify lsp file or use interactive mode.\n");
+	*/
+	fprintf( stderr, "Usage:  %s\n", argv0 );
+	fprintf( stderr, "\tInteractive mode only for now.\n");
+}
+
+/* main() - argv parsing, etc */
+int main( int argc, char ** argv )
+{
+	/*
+	if( argc == 2 )
+	{
+		printf( "Should parse in file %s\n", argv[1] );
+	} else */
+	if( argc == 1 ) {
+		printf( "Generic Common Lithp v%s r%s\n", VERSION, REVISION );
+		printf( "\t\"%s\"\n", TPOTV );
+		printf( "[ctrl]-[d] or \"Exit.\" to exit\n" );
+		cmdloop();
+		printf( "Exiting.\n" );
+	} else {
+		usage( argv[0] );
+		return( -1 );
+	}
+	return( 0 );
+}