Added command line argument option to run as a single command

Added command line option to run the program as a single command
instead of interactive mode

diff --git a/src/main.rs b/src/main.rs
index bab1e52..2154ba5 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@ use std::io::Write;
 use regex::Regex;
 use ansi_term::Colour;
 use ansi_term::Style;
+use std::env;
 
 const ILLEGAL_EXP : &'static str = "Illegal Expression";
 const ERR_PARSING_NOT_MATCH : &'static str = "Error parsing expression! \
@@ -134,38 +135,26 @@ fn evaluate (expr : &str, match_num : &regex::Regex) -> Result<f32,String> {
 }
 
 fn main() {
-       // get a line from input and evaluate it 
-       let mut expr = String::new ();
+
+       let args : Vec<String> = env::args().collect ();
        // regular expression to match a number 
        let match_num = Regex::new (r"^\d+?\.*?\d*?$").unwrap ();
-       // loop until a blank line is received  
-       loop {
-               expr.clear ();  
-               print!("{}", Style::new().bold().paint("evpf>"));
-               io::stdout().flush ().expect (ERR_FLUSHING);
-               // read a line of text
-               io::stdin().read_line (&mut expr).expect (ERR_READING_LINE);
-               // trim the text
-               let expr = expr.trim ();
-
-               if expr == "q" || expr == "Q" {
-               // quit if the expression is q or Qs 
-                       break;
-               } else if expr == "?" || expr == "h" || expr == "H" {
-               // display help text
-                       for text in HELP_TEXT.iter() {
-                               println! ("{}", Colour::Cyan.paint(*text));
+       
+       if args.len () > 1 {
+       // if arguments are provided run in command line mode - i.e. print the 
+       // result and exit      
+               let mut expr = String::new ();
+               let mut i = 0;
+               // create the expression string to evaluate
+               for arg in args.iter() {
+                       if i > 0 {
+                               expr.push_str (&arg);
+                               expr.push_str (" ");
                        }
-
-                       continue;
-               } else if expr == "" {
-               // continue without proceeding
-                       continue;
+                       i += 1;
                }
-               
-               // Evaluate result
+               // evaluate the result 
                let res = evaluate (&expr, &match_num);
-               
                // if Result is OK then print the result in green
                if res.is_ok () {
                        let restxt = format! ("{}: {}", RESULT, 
@@ -176,7 +165,56 @@ fn main() {
                        let errtxt = format! ("{}: {}", ERROR, 
                                                                                        res.unwrap_err());
                        eprintln! ("{}", Colour::Purple.paint (errtxt));
-                       eprintln! ("{}", Colour::Purple.paint (ERROR_HELP));
+               }               
+               
+       } else {
+               // if arguments are not provided run in interactive mode - 
+               // display a prompt and get the expression 
+               // repeat until the user quits
+               
+               // get a line from input and evaluate it 
+               let mut expr = String::new ();
+
+               // loop until a blank line is received  
+               loop {
+                       expr.clear ();  
+                       print!("{}", Style::new().bold().paint("evpf>"));
+                       io::stdout().flush ().expect (ERR_FLUSHING);
+                       // read a line of text
+                       io::stdin().read_line (&mut expr).expect (ERR_READING_LINE);
+                       // trim the text
+                       let expr = expr.trim ();
+
+                       if expr == "q" || expr == "Q" {
+                       // quit if the expression is q or Qs 
+                               break;
+                       } else if expr == "?" || expr == "h" || expr == "H" {
+                       // display help text
+                               for text in HELP_TEXT.iter() {
+                                       println! ("{}", Colour::Cyan.paint(*text));
+                               }
+
+                               continue;
+                       } else if expr == "" {
+                       // continue without proceeding
+                               continue;
+                       }
+                       
+                       // Evaluate result
+                       let res = evaluate (&expr, &match_num);
+                       
+                       // if Result is OK then print the result in green
+                       if res.is_ok () {
+                               let restxt = format! ("{}: {}", RESULT, 
+                                                                                               res.unwrap());
+                               println! ("{}", Colour::Green.paint (restxt));
+                       } else {
+                       // print the error in purple
+                               let errtxt = format! ("{}: {}", ERROR, 
+                                                                                               res.unwrap_err());
+                               eprintln! ("{}", Colour::Purple.paint (errtxt));
+                               eprintln! ("{}", Colour::Purple.paint (ERROR_HELP));
+                       }
                }
        }
 }