From: Harishankar <v.harishankar@gmail.com>
Date: Fri, 29 May 2020 09:26:25 +0000 (+0530)
Subject: Fixed the regular expression - also made the command line robust
X-Git-Tag: 0.1-a~8
X-Git-Url: https://harishankar.org/repos/?p=evpf.git;a=commitdiff_plain;h=8c424fbdf4baf3e27f63b2526def89ddf4ac1b83

Fixed the regular expression - also made the command line robust
Made the command line more robust and fixed the regular expression
to make literal dot using \. instead of . (inadvertent error)
---

diff --git a/src/main.rs b/src/main.rs
index e25413b..c911ca2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
 use std::io;
+use std::io::Write;
 use regex::Regex;
 
 enum Operator { 
@@ -117,26 +118,39 @@ fn main() {
 	// get a line from input and evaluate it 
 	let mut expr = String::new ();
 	// regular expression to match a number 
-	let match_num = Regex::new (r"^\d+?.*?\d*?$").unwrap ();
+	let match_num = Regex::new (r"^\d+?\.*?\d*?$").unwrap ();
 	// loop until a blank line is received	
 	loop {
 		expr.clear ();	
-		println!("Enter an expression (postfix) (blank to quit): ");
+		print!("evpf>");
+		io::stdout().flush ().expect ("Error flushing!");
 		// read a line of text
 		io::stdin().read_line (&mut expr).expect ("Error reading line!");
 		// trim the text
 		let expr = expr.trim ();
-		// quit if the expression is blank
-		if expr == "" { 
+
+		if expr == "q" || expr == "Q" {
+		// quit if the expression is q or Qs 
 			break;
+		} else if expr == "?" || expr == "h" || expr == "H" {
+		// display help text
+			println! ("Type an expression in postfix style to evaluate.");
+			println! ("Example: 4 5 + 12 -");
+			println! ("Supported operators: +, -, *, /");
+			println! ("Type q, Q to quit");
+			continue;
+		} else if expr == "" {
+		// continue without proceeding
+			continue;
 		}
 		
 		let res = evaluate (&expr, &match_num);
 		if res.is_ok () {
-			println! ("Result is : {}", res.unwrap());
+			println! ("Result: {}", res.unwrap());
 		}
 		else {
 			eprintln! ("Error: {}", res.unwrap_err());
+			eprintln! ("Type ? or h or H for help");
 		}
 	}
 }