beautify command line interface

Author: linusboyle

driver/Driver.ml

@@ -218,7 +218,7 @@ let translate fn=
 
 let parse_command () =
     if (Array.length Sys.argv)=1 then
-      print_string usage_msg
+      Arg.usage (Arg.align options) usage_msg
     else
       Arg.parse (Arg.align options) translate usage_msg;;
 

driver/Options.ml

@@ -20,17 +20,6 @@ let usage_msg="\
 USAGE:	l2c [options] <source.ast>
 
 options:
-	-save-temp:		Save temporary intermediate files
-	-coq-parser:		Validated parser by coq
-        -ctemp:                 Output ctemp source
-        -print-parse:           Print parse output
-	-target_dir <dir>:	Set the directory of target files to <dir>
-	-display <file>:	Set the gui specification of l2c display mode
-        -print-display:         Print parsed display model
-	-o <file>:		Indicate the output file name
-	-version:		Print version information
-	-help:			Print this usage message
-
 ";;
 
 let flag_save_temp = ref false;;
@@ -43,16 +32,14 @@ let display_file = ref "";;
 let flag_print_display = ref false;;
 
 let options = [
-    ("-save-temp", Set flag_save_temp, "Save temporary immediate files");
-    ("-coq-parser", Set flag_coq_parser, "Validated parser by coq");
-    ("-ctemp", Set flag_ctemp, "Output ctemp source");
-    ("-print-parse", Set flag_print_parse, "Print parse output");
-    ("-display", Set_string display_file, "The specification file of the l2c display mode");
-    ("-print-display", Set flag_print_display, "Print parsed output of display model");
-    ("-target_dir", Set_string target_dir, "The directory of generated target files");
-    ("-o", Set_string output_file, "Indicate the output file name");
-    ("-version", Unit (fun()->(print_string version_msg)), "Print version information");
-    ("-help", Unit (fun()->(print_string usage_msg)), "Print this usage message");
+    ("-save-temp", Set flag_save_temp, "    Save temporary immediate files");
+    ("-coq-parser", Set flag_coq_parser, "  Validated parser by coq");
+    ("-ctemp", Set flag_ctemp, "    Output ctemp source");
+    ("-print-parse", Set flag_print_parse, "    Print parse output");
+    ("-display", Set_string display_file, "<file> The specification file of the l2c display mode");
+    ("-print-display", Set flag_print_display, "    Print parsed output of display model");
+    ("-target_dir", Set_string target_dir, "<dir>    The directory of generated target files");
+    ("-o", Set_string output_file, "<file>    Indicate the output file name");
+    ("-version", Unit (fun()->(print_string version_msg)), "    Print version information");
+    ("-help", Unit (fun()->(print_string usage_msg)), " Print this usage message");
 ];;
-
-