module examples/runnable/string_parsing

-- Demonstrates string-to-number parsing with Option types

-- Shows how to safely parse user input using pattern matching

import std/string (stringToInt, stringToFloat)

import std/option (Option, Some, None, getOrElse)

import std/io (println)

-- Parse an age string and validate it

pure func parseAge(input: string) -> Option[int] {

match stringToInt(input) {

Some(age) => if age >= 0 then Some(age) else None,

None => None

}

}

-- Parse a price string (handles decimals)

pure func parsePrice(input: string) -> Option[float] {

stringToFloat(input)

}

-- Test valid integer parsing

pure func testValidInt() -> string {

match stringToInt("42") {

Some(n) => "✓ stringToInt(\"42\") = Some(42)",

None => "✗ Failed to parse valid int"

}

}

-- Test invalid integer parsing

pure func testInvalidInt() -> string {

match stringToInt("abc") {

Some(n) => "✗ Should have returned None",

None => "✓ stringToInt(\"abc\") = None (expected)"

}

}

-- Test valid float parsing

pure func testValidFloat() -> string {

match stringToFloat("3.14") {

Some(f) => "✓ stringToFloat(\"3.14\") = Some(3.14)",

None => "✗ Failed to parse valid float"

}

}

-- Test invalid float parsing

pure func testInvalidFloat() -> string {

match stringToFloat("not-a-number") {

Some(f) => "✗ Should have returned None",

None => "✓ stringToFloat(\"not-a-number\") = None (expected)"

}

}

-- Test getOrElse with default value

pure func testDefault() -> string {

let result = getOrElse(stringToInt("invalid"), 99);

"✓ getOrElse with default: 99"

}

-- Test age validation

pure func testAgeValidation() -> string {

match parseAge("25") {

Some(age) => "✓ Valid age: 25",

None => "✗ Age validation failed"

}

}

-- Test negative age rejection

pure func testNegativeAge() -> string {

match parseAge("-5") {

Some(age) => "✗ Should reject negative age",

None => "✓ Negative age rejected (expected)"

}

}

-- Main function demonstrating the parsing functions

export func main() -> () ! {IO} {

{ println("=== String Parsing Examples (M-DX10) ===");

println("");

println("Integer parsing:");

println(testValidInt());

println(testInvalidInt());

println("");

println("Float parsing:");

println(testValidFloat());

println(testInvalidFloat());

println("");

println("Option helpers:");

println(testDefault());

println("");

println("Validation:");

println(testAgeValidation());

println(testNegativeAge());

()

}

}