list of programming languages
A database query is expensive. It travels the network, the database parses the SQL, the planner picks the plan, the engine reads the pages, and the results return over the wire. The whole trip takes the milliseconds, and the same query runs thousands of times. The result rarely changes. The cache stores the result, and…
A closure is an anonymous function that can capture the variables from the scope where it is defined. It is the fundamental tool for the higher-order functions, the callbacks, and the concise inline logic. The |x| x + 1 is a closure that takes the x and returns the x + 1, and unlike the…
NULL is not a value. It is the absence of a value. It does not equal anything—not even itself. It does not compare greater or less than anything. It propagates through arithmetic and string operations, turning everything it touches into NULL. This behavior is correct according to the SQL standard, but it is inconvenient in…
Immutability is the practice of never modifying a value after it is created. Instead of changing an object, you create a new one with the change applied. This sounds like a small discipline, but it has large consequences: immutable data is safe to share, safe to compare by reference, safe to use in concurrent contexts,…
These three functions are the individual axis scaling functions in CSS transforms. Each one scales an element along a specific axis: X (horizontal), Y (vertical), or Z (depth). Overview of Functions Function Axis Equivalent Effect scaleX() Horizontal scale3d(s, 1, 1) Stretches width scaleY() Vertical scale3d(1, s, 1) Stretches height scaleZ() Depth scale3d(1, 1, s) Stretches…
A unit test should test one thing. When the unit under the test depends on the database, the network, the clock, or the file system, the test must isolate the unit from those dependencies. Otherwise the test is slow, flaky, and coupled to the external systems. Test doubles are the objects that stand in for…
JavaScript has one number type — a 64-bit floating-point value. There’s no separate integer type (except BigInt). Understanding how it behaves — including its limits and quirks — is essential for writing correct numeric code. Key point: All JavaScript numbers are IEEE 754 double-precision floating-point. This means integers up to 2^53 are exact, but floating-point…
A traditional session lives on the server. The user logs in, the server creates the session record, and the session ID goes into the cookie. The next request carries the cookie, and the server looks up the session in the store. The lookup is the state, and the state is the scaling problem: the session…
A closure captures the variables it uses from the surrounding scope. By default, the compiler infers the least restrictive capture: an immutable borrow if the closure only reads the variable, a mutable borrow if it modifies it, and a move if the closure takes ownership. The inference is convenient for the closures that are called…
A string in SQL is a sequence of characters. In practice, it is rarely clean. It has leading and trailing whitespace, inconsistent casing, substrings that need extraction, parts that need concatenation, and lengths that need measuring. SQL provides a set of string functions for these operations, and although the exact names vary slightly between databases,…