Note: All of this capability is implemented except the special my name.
Now that we have literals and variables, we can construct more complex expressions that use operators, methods and functions calls to calculate new values. Although the expression examples on this page work with integer and floating point values, similar expressions can be formulated that manipulate values of other types.
Integer and floating point numbers may be computed using arithmetic operators:
- Subtract (or negate when used as a prefix operator)
- Modulo (remainder)
-12 + 14 // 2 6 / 5 // 1 -4 % 3 // -1 (where -4/3 --> -1, truncating towards zero) 2*2 + 2*3 // 10 (standard algebraic operator precedence) 2 * (4 + 1) // 10 (parentheses override operator precedence)
Additional calculations can be performed using method calls. The name of the desired method follows the object value, separated by the dot operator ('.'):
(-1).abs // 1 (the absolute value, making a number positive) (pi/2).sin // 1.0 (trigonometric sine function)
Sometimes, a method may require additional values. These argument values are specified within parentheses following the method's name.
4.max(5) // 5 (returns the larger of the two numbers)
Method calls are very common and convenient. It is helpful to know that:
- The logic a method performs depends on the type of the value it is applied to. Thus, a method named 'max' applied to an integer is actually a different method than when 'max' is applied to a floating point number. Every type defines the names and logic for all methods it supports. An error results when trying to use a method not implemented by the value's type.
- The arithmetic operators introduced earlier (e.g., + for add)
are implemented under the covers using number type methods:
// The method name equivalent for the + operator is `+` // The method name is enclosed in backticks since it includes punctuation 3+4 // is actually: 3.`+`(4)
Note: The arguments to a function or method call are evaluated in left-to-right order. This is also true for tuples.
Note: Inside any argument on a method call, the special name my may be used. Its value is the same as the object of the method call. This can be helpful to call helper methods on the object to prepare other argument values.
Function calls are very much like method calls, except they are not applied to a value in the same way. Instead of specifying a value, dot operator, and a method name, one simply specifies the function name followed by any comma-separated arguments in parentheses.
To convert a number from one type to another, enclose the number in square brackets with the intended type on the left:
imm six = i32[6u8] // Converts 8-bit unsigned integer to 32-bit signed integer imm sixf = f64[six] // Converts 32-bit signed integer to 64-bit floating point number
If the receiving number type is a smaller size, numeric information may be lost.
The bitwise operators operate on true/false values:
true | (false & true) // true true ^ ~true // true
These bitwise operators may also be used on unsigned integers, as they are viewed as a collection of true/false bits.
0xE0u | 0xB8u // 0xF8u
The shifting of an unsigned integer's bit is accomplished using the << and >> operators:
0x0Cu << 1 // 0x18, after shifting bits left once
An 'lval'-based expression is one where the expression to the "left" represents a memory "container" which holds a value. Lval-based expressions will change the stored value. The assignment expression introduced on the previous page is lval-based, as examples specified a variable to the left of the =.
Parallel assignment makes it possible to simultaneously assign multiple values to multiple variables. This can be convenient when swapping the values held by two variables:
// Swap the variable values for a and b a,b = b,a
This is also useful for capturing multiple values returned by a function or method call:
min, max = minmax(5, 4)
When used to the left of an lval, ++ will increment the number and -- will decrement it.
mut cnt = 10 ++cnt // 11 --cnt // 10
When used to the right of an lval, it will still increment and decrement, but the expression will return the original value.
mut cnt = 10 imm x = cnt++ // x is 10, cnt is 11
The arithmetic assignment operators (e.g., '+=', '-=', '*=', '/=') offer a convenient way to update an existing stored value:
counter = 3 counter += 1 // 4. Equivalent to: counter = counter + 1
Logical assignment operators
These work similarly to the arithmetic assignment operators:
mut flags = 0xC0u flags |= 0x01u // 0xC1u flags >>= 1 // 0x60u
Other Expression Operators
Cone supports several more expression operators. Descriptions may be found in the chapters relevant to their common use: