diff options
| -rw-r--r-- | doc/manual.rst | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/doc/manual.rst b/doc/manual.rst index a5a1c7cb2..ca32c9c61 100644 --- a/doc/manual.rst +++ b/doc/manual.rst @@ -618,6 +618,55 @@ The grammar's start symbol is ``module``. +Order of evaluation +=================== + +Order of evaluation is strictly left-to-right, inside-out as it is typical for most others +imperative programming languages: + +.. code-block:: nim + :test: "nim c $1" + + var s = "" + + proc p(arg: int): int = + s.add $arg + result = arg + + discard p(p(1) + p(2)) + + doAssert s == "123" + + +Assignments are not special, the left-hand-side expression is evaluated before the +right-hand side: + +.. code-block:: nim + :test: "nim c $1" + + var v = 0 + proc getI(): int = + result = v + inc v + + var a, b: array[0..2, int] + + proc someCopy(a: var int; b: int) = a = b + + a[getI()] = getI() + + doAssert a == [1, 0, 0] + + v = 0 + someCopy(b[getI()], getI()) + + doAssert b == [1, 0, 0] + + +Rationale: Consistency with overloaded assignment or assignment-like operations, +``a = b`` can be read as ``performSomeCopy(a, b)``. + + Types ===== |