New init template

This new template uses newer Cairo features (loops), and additionally is both runnable and testable.

Author: mkaput

examples/hello_world/README.md

@@ -1,3 +1,16 @@
 # `hello_world`
 
 This example is a result of running `scarb new --no-vcs hello_world`.
+This template can be both run and tested, try running following commands:
+
+```shell
+scarb build
+```
+
+```shell
+scarb test
+```
+
+```shell
+scarb cairo-run --available-gas 200000
+```

examples/hello_world/Scarb.toml

@@ -5,4 +5,4 @@ version = "0.1.0"
 # See more keys and their definitions at https://docs.swmansion.com/scarb/docs/reference/manifest.html
 
 [dependencies]
-alexandria_math = { git = "https://github.com/keep-starknet-strange/alexandria.git" }
+# foo = { path = "vendor/foo" }

examples/hello_world/src/lib.cairo

@@ -1,16 +1,28 @@
-use alexandria_math::fibonacci::fib;
+fn main() -> felt252 {
+    fib(16)
+}
 
-fn double_fib(a: felt252, b: felt252, n: felt252) -> felt252 {
-    2 * fib(a, b, n)
+fn fib(mut n: felt252) -> felt252 {
+    let mut a: felt252 = 0;
+    let mut b: felt252 = 1;
+    loop {
+        if n == 0 {
+            break a;
+        }
+        n = n - 1;
+        let temp = b;
+        b = a + b;
+        a = temp;
+    }
 }
 
 #[cfg(test)]
 mod tests {
-    use super::double_fib;
+    use super::fib;
 
     #[test]
     #[available_gas(100000)]
     fn it_works() {
-        assert(double_fib(0, 1, 16) == 1974, 'it works!');
+        assert(fib(16) == 987, 'it works!');
     }
 }

scarb/src/ops/new.rs

@@ -139,10 +139,32 @@ fn mk(
         fsx::write(
             source_path,
             indoc! {r#"
-                fn fib(a: felt252, b: felt252, n: felt252) -> felt252 {
-                    match n {
-                        0 => a,
-                        _ => fib(b, a + b, n - 1),
+                fn main() -> felt252 {
+                    fib(16)
+                }
+
+                fn fib(mut n: felt252) -> felt252 {
+                    let mut a: felt252 = 0;
+                    let mut b: felt252 = 1;
+                    loop {
+                        if n == 0 {
+                            break a;
+                        }
+                        n = n - 1;
+                        let temp = b;
+                        b = a + b;
+                        a = temp;
+                    }
+                }
+
+                #[cfg(test)]
+                mod tests {
+                    use super::fib;
+
+                    #[test]
+                    #[available_gas(100000)]
+                    fn it_works() {
+                        assert(fib(16) == 987, 'it works!');
                     }
                 }
             "#},