Functional languages like Haskell and its antecedent Miranda grew out of the mathematical concept of lambda calculus. From the Wikipedia page:
Lambda calculus (also written as λ-calculus or called "the lambda calculus") is a formal system in mathematical logic for expressing computation by way of variable binding and substitution.
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Lambda calculus has played an important role in the development of the theory of programming languages. The most prominent counterparts to lambda calculus in computer science are functional programming languages, which essentially implement the calculus (augmented with some constants and datatypes). Beyond programming languages, the lambda calculus also has many applications in proof theory. A major example of this is the Curry–Howard correspondence, which gives a correspondence between different systems of typed lambda calculus and systems of formal logic.
Because of this history, the syntaxes of these functional languages (and functional elements of more imperative languages) are strongly influenced by the mathematical notation used by lambda calculus.
The precision with which both mathematical notations and computer languages can describe requirements and the precision with which computers require their instructions to be written correlate well with each other. The imprecision of natural language however creates a huge barrier to it's use for programming computers. Even the (arguably) most successful Natural language programming environments such as Wolfram Alpha need significant domain experience to be used effectively.
