Precondition
A precondition is a condition or requirement that must be satisfied before an operation, process, or action can proceed correctly.
Modern C, Third Edition
A platform precondition is a required property or capability of the execution environment that must hold for code to be valid or executable.
- How it is used
- Identifies requirements that must hold for C code to run correctly, especially platform capabilities that should be checked before compilation proceeds.
- How deep it goes
- Works through compile-time guards and static assertions, then distinguishes argument checks from checks of operations that may exhaust resources.
- Examples
- Uses an Annex K #if/#error guard, a type-size static_assert, and an asserted argument ordering in a recursive greatest-common-divisor function.
- What you can do after
- Apply precondition checks to reject unsupported platforms at compile time and make function-call requirements explicit.
Software Design for Python Programmers
A precondition is a state or event that must hold or have occurred before a use case can begin.
- How it is used
- Uses preconditions to specify required starting states for use cases and callable interfaces.
- How deep it goes
- Explains Boolean conditions, caller responsibility, documentation, guarantees, and CircularBuffer predicates, but not formal verification.
- Examples
- Demonstrates full and empty CircularBuffer checks through add() and remove() operations.
- What you can do after
- Apply it by documenting callable requirements and checking them before operations that depend on valid starting states.
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Object-Oriented Software Design in C++
A design principle stating that a function caller must establish the function's precondition before invoking it.
- How it is used
- Uses preconditions to define caller obligations before function calls, subclass overrides, and use-case execution.
- How deep it goes
- Defines Boolean conditions, demonstrates checks in CircularBuffer, and examines inheritance constraints without developing formal contract machinery.
- Examples
- Demonstrates buffer capacity checks, Shipment cost validation, polymorphic shipping tests, and Search Catalogue use-case descriptions.
- What you can do after
- Evaluate function and subclass contracts by identifying caller checks and detecting strengthened overriding preconditions.
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Clojure: The Essential Reference
A precondition is a Boolean assertion that must hold before a function body executes.
- How it is used
- Uses preconditions to enforce input requirements when calling functions defined with `defn`.
- How deep it goes
- Defines placement and failure behavior, then demonstrates input checks; does not explore assertion internals.
- Examples
- Checks a `save!` item’s map shape, integer multiplier, and permitted width; shows failures for invalid input.
- What you can do after
- Apply it via Clojure `defn` to reject inputs that violate a function’s requirements before its body runs.
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Modern C
A precondition is a condition that must hold before a function or operation is invoked.
- How it is used
- Constrains function calls and execution platforms so invalid assumptions become explicit failures.
- How deep it goes
- Defines argument and platform conditions, demonstrates runtime and compile-time checks, and defers fuller assert details.
- Examples
- Uses Euclid's gcd recursion, gcd2(18, 30), #if/#error, and a static_assert comparing double and long double sizes.
- What you can do after
- Apply preconditions with assert, #if/#error, and static_assert to reject invalid calls or unsupported platforms.
Simple Object-Oriented Design: Create clean, maintainable applications
A precondition is a requirement that must hold before an operation can execute correctly.
- How it is used
- Defines minimum method-input requirements to prevent invalid calls and inconsistent execution.
- How deep it goes
- Explains invalid-input choices and distinguishes preconditions from business validation rules without detailing implementation mechanics.
- Examples
- Uses adding an employee to a training course and handling a null employee input.
- What you can do after
- Evaluate/understand whether invalid input should halt execution or be safely tolerated by an operation.
Learn Haskell by Example
A precondition is a condition that causes generated test cases failing the condition to be discarded before the property is evaluated.
- How it is used
- Filters irrelevant generated inputs before evaluating a QuickCheck property.
- How deep it goes
- Defines implication-based filtering and reports discarded cases, but defers generator redesign and coverage measurement to separate techniques.
- Examples
- Uses a sorting property requiring lists with at least two elements and reports 43 discarded cases.
- What you can do after
- Apply it via QuickCheck's `==>` operator to exclude irrelevant generated test cases.
Functional Design and Architecture: Examples in Haskell
A precondition is an input condition that must hold before a user scenario or system operation begins.
- How it is used
- Uses preconditions to state scenario entry requirements and control which generated inputs reach tested logic.
- How deep it goes
- Explains requirements-level meaning and property-testing failure mechanics, then lists generator adjustments without developing formal contract theory.
- Examples
- Uses a launched game, bounded labyrinth dimensions, arbitrary integer pairs, and QuickCheck rejection behavior as examples.
- What you can do after
- Diagnose property tests that reject excessive generated inputs and choose narrower, broader, or better-distributed test data.
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Related concepts
- assertionused by · A software assertion is an executable check of an expected condition or property that signals failure when the check does not hold.
- QuickCheckused by · QuickCheck is a property-based testing library that generates test inputs from specifications, checks their properties, and may minimize failing counterexamples.
- validation rulecontrasts with · A validation rule is a condition or constraint that determines whether data, a state, or an operation satisfies specified requirements.
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