Functions.

examples/functions_test.fun

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+#!/usr/bin/env fun
+
+// Functions test: definitions, calls, parameters, locals, returns, and if/else.
+
+print("=== Functions test start ===")
+
+fun add(a, b)
+  return a + b
+
+fun abs(x)
+  if (x < 0)
+    return -x
+  else
+    return x
+
+fun sum3(a, b, c)
+  // local typed declaration
+  number t = a + b
+  return t + c
+
+fun id(x)
+  return x
+
+// Calls in expressions
+print(add(2, 3))             // expect 5
+print(add(10, -3))           // expect 7
+print(abs(-7))               // expect 7
+print(abs(4))                // expect 4
+print(sum3(1, 2, 3))         // expect 6
+print(add(add(1, 2), 3))     // expect 6
+print(id(42))                // expect 42
+
+// Call as statement (result discarded)
+add(100, 23)
+
+// Globals interacting with functions
+number n = 5
+print(add(n, 10))            // expect 15
+
+print("=== Functions test end ===")