83 lines
2.6 KiB
Markdown
83 lines
2.6 KiB
Markdown
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Logic Operators
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==============
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{{#include ../links.md}}
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Comparison Operators
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-------------------
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Comparing most values of the same data type work out-of-the-box for all [standard types] supported by the system.
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However, if using a [raw `Engine`] without loading any [packages], comparisons can only be made between a limited
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set of types (see [built-in operators]).
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```rust
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42 == 42; // true
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42 > 42; // false
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"hello" > "foo"; // true
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"42" == 42; // false
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```
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Comparing two values of _different_ data types, or of unknown data types, always results in `false`,
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except for '`!=`' (not equals) which results in `true`. This is in line with intuition.
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```rust
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42 == 42.0; // false - i64 cannot be compared with f64
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42 != 42.0; // true - i64 cannot be compared with f64
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42 > "42"; // false - i64 cannot be compared with string
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42 <= "42"; // false - i64 cannot be compared with string
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let ts = new_ts(); // custom type
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ts == 42; // false - types cannot be compared
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ts != 42; // true - types cannot be compared
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```
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Boolean operators
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-----------------
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| Operator | Description |
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| -------- | ------------------------------------- |
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| `!` | Boolean _Not_ |
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| `&&` | Boolean _And_ (short-circuits) |
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| `\|\|` | Boolean _Or_ (short-circuits) |
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| `&` | Boolean _And_ (doesn't short-circuit) |
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| `\|` | Boolean _Or_ (doesn't short-circuit) |
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Double boolean operators `&&` and `||` _short-circuit_, meaning that the second operand will not be evaluated
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if the first one already proves the condition wrong.
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Single boolean operators `&` and `|` always evaluate both operands.
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```rust
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this() || that(); // that() is not evaluated if this() is true
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this() && that(); // that() is not evaluated if this() is false
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this() | that(); // both this() and that() are evaluated
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this() & that(); // both this() and that() are evaluated
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```
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Compound Assignment Operators
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----------------------------
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```rust
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let number = 5;
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number += 4; // number = number + 4
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number -= 3; // number = number - 3
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number *= 2; // number = number * 2
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number /= 1; // number = number / 1
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number %= 3; // number = number % 3
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number <<= 2; // number = number << 2
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number >>= 1; // number = number >> 1
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```
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The `+=` operator can also be used to build [strings]:
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```rust
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let my_str = "abc";
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my_str += "ABC";
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my_str += 12345;
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my_str == "abcABC12345"
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```
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