examples: cleanup and shorten mini_calculator_recursive_descent.v to 98 lines (#23847)

examples/mini_calculator_recursive_descent.v

@@ -14,17 +14,17 @@ struct Parser {
 	textscanner.TextScanner
 }
 
-fn (mut p Parser) parse_expression() !f64 {
-	mut result := p.parse_term()!
+fn (mut p Parser) expr() !f64 {
+	mut result := p.term()!
 	for {
 		p.skip_whitespace()
 		c := p.peek_u8()
 		if c == `+` {
 			p.next()
-			result += p.parse_term()!
+			result += p.term()!
 		} else if c == `-` {
 			p.next()
-			result -= p.parse_term()!
+			result -= p.term()!
 		} else {
 			break
 		}
@@ -32,17 +32,17 @@ fn (mut p Parser) parse_expression() !f64 {
 	return result
 }
 
-fn (mut p Parser) parse_term() !f64 {
-	mut result := p.parse_factor()!
+fn (mut p Parser) term() !f64 {
+	mut result := p.factor()!
 	for {
 		p.skip_whitespace()
 		c := p.peek_u8()
 		if c == `*` {
 			p.next()
-			result *= p.parse_factor()!
+			result *= p.factor()!
 		} else if c == `/` {
 			p.next()
-			result /= p.parse_factor()!
+			result /= p.factor()!
 		} else {
 			break
 		}
@@ -50,14 +50,14 @@ fn (mut p Parser) parse_term() !f64 {
 	return result
 }
 
-fn (mut p Parser) parse_factor() !f64 {
+fn (mut p Parser) factor() !f64 {
 	p.skip_whitespace()
 	c := p.peek_u8()
 	if c.is_digit() {
-		return p.parse_number()
+		return p.number()
 	} else if c == `(` {
 		p.next()
-		result := p.parse_expression()!
+		result := p.expr()!
 		p.skip_whitespace()
 		if p.next() != `)` {
 			return error('Expected closing parenthesis')
@@ -67,7 +67,7 @@ fn (mut p Parser) parse_factor() !f64 {
 	return error('Expected number or opening parenthesis')
 }
 
-fn (mut p Parser) parse_number() !f64 {
+fn (mut p Parser) number() !f64 {
 	start := p.pos
 	for {
 		c := p.peek_u8()
@@ -77,24 +77,20 @@ fn (mut p Parser) parse_number() !f64 {
 		}
 		break
 	}
-	num_str := p.input[start..p.pos]
-	return strconv.atof64(num_str) or { return error('Invalid number') }
+	return strconv.atof64(p.input[start..p.pos]) or { error('Invalid number') }
 }
 
-println('Please enter the expression you want to calculate, e.g. `2 * (5-1)` .')
-println("Enter 'exit' or 'EXIT' to quit.")
-mut expr_count := 0
-for {
-	expr_count++
-	input := os.input_opt('[${expr_count}] ') or {
+println('Enter expressions to calculate, e.g. `2 * (5-1)` or `exit` to quit.')
+for i := 1; true; i++ {
+	input := os.input_opt('[${i}] ') or {
 		println('')
 		break
 	}.trim_space()
-	if input in ['exit', 'EXIT'] {
+	if input.to_upper() == 'EXIT' {
 		break
 	}
 	mut parser := Parser{textscanner.new(input)}
-	result := parser.parse_expression() or {
+	result := parser.expr() or {
 		println('Error: ${err}')
 		continue
 	}