Data commit

Task/Call-a-function/EMal/call-a-function.emal

@@ -0,0 +1,80 @@
+fun task = void by text about, fun code
+  writeLine(0U00b7 + " " + about)
+  code()
+end
+fun answer = void by var message do writeLine("  " + message) end
+# few definitions
+fun noArgumentsFunction = int by block do return 97 end
+fun fixedArgumentsFunction = void by var a, var b do end
+fun variadicFunction = void by text a, some var values do end
+fun funArgumentFunction = var by fun f, var b do return f() + b end
+task("Calling a function that requires no arguments", void by block
+  answer("Is supported.")
+  noArgumentsFunction()
+end)
+task("Calling a function with a fixed number of arguments", void by block
+  answer("Is supported.")
+  fixedArgumentsFunction(97, 3.14)
+end)
+task("Calling a function with optional arguments", void by block
+  answer("Not supported in EMal.")
+end)
+task("Calling a function with a variable number of arguments", void by block
+  answer("Variadic functions are supported.")
+  variadicFunction("mandatory", 97, 3.14)
+  variadicFunction("mandatory", 97)
+end)
+task("Calling a function with named arguments", void by block
+  answer("Not supported in EMal.")
+end)
+task("Using a function in statement context", void by block
+  answer("Is supported.")
+  if true do noArgumentsFunction()
+  else do fixedArgumentsFunction(97, 3.14) end
+end)
+task("Using a function in first-class context within an expression", void by block
+  answer("Functions are first class, can be passed as arguments and returned.")
+  answer(funArgumentFunction(noArgumentsFunction, 3.14))
+end)
+task("Obtaining the return value of a function", void by block
+  answer("Is supported.")
+  int value = noArgumentsFunction()
+  answer(value)
+end)
+task("Distinguishing built-in functions and user-defined functions", void by block
+  answer("No distinction.")
+end)
+task("Distinguishing subroutines and functions", void by block
+  answer("No distinction, we support void return type.")
+end)
+task("Stating whether arguments are passed by value or by reference", void by block
+  answer("Pass by value, but text, blob, objects hold a reference.")
+end)
+task("Is partial application possible and how", void by block
+  answer("Is supported.")
+  ^|I had some confusion about partial application and currying, thanks to these links:
+   |  https://stackoverflow.com/questions/218025/what-is-the-difference-between-currying-and-partial-application
+   |  https://web.archive.org/web/20161023205431/http://www.uncarved.com/articles/not_curryin
+   |^
+  # Partial applying
+  fun add = int by int a, int b do return a + b end
+  fun partial = fun by fun f, int a
+    return int by int b
+      return add(a, b)
+    end
+  end
+  fun add7 = partial(add, 7)
+  answer(add(7, 5))
+  answer(add7(5))
+  # Currying
+  fun addN = fun by int n
+    return int by int x
+      return x + n
+    end
+  end
+  fun plus = int by int a, int b
+    fun addA = addN(a)
+    return addA(b)
+  end
+  answer(plus(7, 5))
+end)