use std::io;
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! \
+ Must be a number or operator (+,-,* or /)";
+const ERR_POSTFIX_INCOMPLETE : &'static str = "Postfix expression incomplete!";
+const ERR_FLUSHING : &'static str = "Error flushing!";
+const ERR_READING_LINE : &'static str = "Error reading line!";
+const HELP_TEXT : [&str ; 4] =
+ ["Type an expression in postfix style to evaluate.",
+ "Example: 4 5 + 12 -",
+ "Supported operators: +, -, *, /",
+ "Type q, Q to quit"
+ ];
+
+const RESULT : &'static str = "Result";
+const ERROR : &'static str = "Error";
+const ERROR_HELP : &'static str = "Type ? or h or H for help";
+
+// Describe an operator - one of add, subtract, multiply or divide
enum Operator {
ADD,
SUB,
// if nothing - panic with error
let n1 = t.pop ();
if n1.is_none () {
- return Err ("Illegal expression".to_string());
+ return Err (ILLEGAL_EXP.to_string());
}
// pop the stack for the first operand
// if nothing - panic with error
let n2 = t.pop ();
if n2.is_none () {
- return Err ("Illegal expression!".to_string());
+ return Err (ILLEGAL_EXP.to_string());
}
let num1 = n1.unwrap().value;
}
// if word doesn't match either operator or number then panic.
else {
- return Err ("Error parsing expression! \
- Must be a number or operator (+,-,* or /)".to_string());
+ return Err (ERR_PARSING_NOT_MATCH.to_string());
}
}
}
if ops.len () > 1 {
// if the stack has more than one value, it means that the postfix
// expression is not complete - so display the stack status
- return Err ("Postfix expression incomplete!".to_string());
+ return Err (ERR_POSTFIX_INCOMPLETE.to_string());
} else {
// stack has only one item which is the result so display it
let res = ops[0].value;
}
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!("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 ();
-
- 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;
+
+ 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 (" ");
+ }
+ i += 1;
}
-
+ // evaluate the result
let res = evaluate (&expr, &match_num);
+ // if Result is OK then print the result in green
if res.is_ok () {
- println! ("Result: {}", res.unwrap());
- }
- else {
- eprintln! ("Error: {}", res.unwrap_err());
- eprintln! ("Type ? or h or H for help");
+ 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));
+ }
+
+ } 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));
+ }
}
}
}
projects / evpf.git / blobdiff