Name of application entry point

proposals/p2265.md

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+# Name of application entry point
+
+<!--
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+-->
+
+[Pull request](https:/carbon-language/carbon-lang/pull/2265)
+
+<!-- toc -->
+
+## Table of contents
+
+- [Abstract](#abstract)
+- [Problem](#problem)
+- [Background](#background)
+- [Proposal](#proposal)
+- [Rationale](#rationale)
+- [Alternatives considered](#alternatives-considered)
+ - [Use the name `Run`](#use-the-name-run)
+
+<!-- tocstop -->
+
+## Abstract
+
+This proposal presents a bit of background information on entry point names from
+other languages and draws the conclusion that Carbon should adopt `Main` as its
+entry point name from the little objective information and trends that can be
+deduced.
+
+## Problem
+
+While it isn't a pressing need, a standardization on the name of the entry point
+will be necessary as execution starts from a consistent and known place.
+
+## Background
+
+Within Carbon community based discussions, the two names that have merited
+discussion so far have been `Main` and `Run`.
+
+Overwhelmingly, the majority of mainstream programming languages use a version
+of `Main` as their entry point (although capitalization varies based on the
+language's standards). Some of the most prominent examples are C, C++, D, Zig,
+Rust, Kotlin, Java, C#, Go, and Haskell.
+
+Meanwhile, `Run` seems to be far less common as an application entry point,
+although it does see more use as a framework entry point, likely aided by its
+place in the English language as a "command" word. Notably it is also used by
+Docker to begin running a container process.
+
+## Proposal
+
+Carbon officially adopts the name `Main` for its application entry point.
+
+## Rationale
+
+By going with `Main` the entry point both
+[adheres to the principle of least surprise](https:/carbon-language/carbon-lang/blob/trunk/docs/project/goals.md#code-that-is-easy-to-read-understand-and-write)
+and provides
+[familiarity for experienced C++ developers with a gentle learning curve](https:/carbon-language/carbon-lang/blob/trunk/docs/project/goals.md#interoperability-with-and-migration-from-existing-c-code).
+
+## Alternatives considered
+
+Options for alternatives are limitless although few others are as standardized
+or likely to receive support due to familiarity and convention.
+
+Additionally, options representing a more dramatic paradigm shift such as (a)
+user defined entry point(s) or similar structural changes have not been
+discussed as they are outside of the scope of this proposal.
+
+### Use the name `Run`
+
+We considered using the name `Run` instead of `Main`. One motivation for this is
+that we typically want function names to be verb phrases rather than noun
+phrases. Another is that the entry point function is seldom the main, or most
+important, function in the program, so the name `Main` is an anachronism from a
+time when programs were much smaller.
+
+However, the benefits of selecting a new name are minor, and the benefits of
+following established conventions are more significant, especially given our
+goal of familiarity for experienced C++ developers.