Class-based programming: Difference between revisions

Revision as of 08:28, 13 September 2016

Revision as of 16:45, 14 January 2017

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:''Let <math>q(x)</math> be a property provable about objects <math>x</math> of type <math>T</math>. Then <math>q(y)</math> should be provable for objects <math>y</math> of type <math>S</math>, where <math>S</math> is a subtype of <math>T</math>.''

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<blockquote>''Subtype Requirement'': Let {{tmath| \phi(x) }} be a property provable about objects {{mathtmath| x }} of type {{mathtmath| T}}. Then {{tmath| \phi(y) }} should be true for objects {{mathtmath| y }} of type {{mathtmath| S }} where {{mathtmath| S }} is a subtype of {{mathtmath| T}}. </blockquote>

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:''Let {{math| '''q(x)''' }} be a property provable about objects {{math| '''x''' }} of type {{math| '''T'''. }} Then {{math| '''q(y)''' }} should be provable for objects {{math| '''y''' }} of type {{math| '''S''', }} where {{math| '''S''' }} is a subtype of {{math| '''T'''. }}''