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content/variables/page.md

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+# Variables
+
+Nimrod supports three different types of variables, `let`, `var`, and `const`. As with most things, multiple variables can be declared in the same section.
+
+~~~ nimrod
+proc getAlphabet(): string =
+  result = ""
+  for letter in 'a'..'z':
+    result.add(letter)
+
+const abcs = getAlphabet()
+
+var
+  a = "foo"
+  b = 0
+
+let
+  c = "foo"
+  d = 5
+
+a.add "bar" # This is fine because ``a`` is mutable.
+b.inc # This is also fine.
+
+c.add "bar" # This will result in an error.
+d.inc # As will this.
+~~~
+
+~~~
+$ nimrod c --verbosity:2 ./assignment.nim
+a20.nim(19, 0) Error: for a 'var' type a variable needs to be passed
+  c.add "bar" # This will result in an error.
+  ^
+~~~
+
+Without `--verbosity:2` only the error will be shown.
+
+A `const` variable's value will be evaluated at compile-time, so if you inspect the C sources, you'll see the following line:
+
+~~~ C
+STRING_LITERAL(TMP129, "abcdefghijklmnopqrstuvwxyz", 26);
+~~~
+
+The limitation with this is that procedures which are evaluated at compile-time cannot interface with C because there is no compile-time foreign function interface at this time.
+
+As seen in the example, `var` variables are standard mutable variables, you can modify them after they've been assigned. `let` variables on the other hand are immutable variables. This means you can assign to them at creation time and can't change them later on. The difference between `let` and `const` is that a `const`'s expression must be evaluated at compile-time, a `let`'s expression doesn't have this requirement.