From 07bf9008a0698d2ada09fe7db471adb349f1703c Mon Sep 17 00:00:00 2001 From: Marshall Lochbaum Date: Fri, 16 Apr 2021 15:44:04 -0400 Subject: =?UTF-8?q?Specification=20for=20Catch=20(=E2=8E=8A)?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- docs/spec/evaluate.html | 1 + 1 file changed, 1 insertion(+) (limited to 'docs/spec/evaluate.html') diff --git a/docs/spec/evaluate.html b/docs/spec/evaluate.html index 892aa7a5..9e221c53 100644 --- a/docs/spec/evaluate.html +++ b/docs/spec/evaluate.html @@ -7,6 +7,7 @@

Specification: BQN evaluation

This page describes the semantics of the code constructs whose grammar is given in grammar.md. The formation rules there are not named, and here they are identified by either the name of the term or by copying the rule entirely if there are several alternative productions.

Here we assume that the referent of each identifier, or equivalently the connections between identifiers, have been identified according to the scoping rules.

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Errors described in this page are "evaluation errors" and can be caught by the Catch (⎊) modifier. If an error is caught, evaluation halts without attempting to complete any in-progress node, and is restarted as part of the execution of Catch.

Programs and blocks

The result of parsing a valid BQN program is a PROGRAM, and the program is run by evaluating this term.

A PROGRAM or BODY is a list of STMTs, which are evaluated in program order. A result is always required for BODY nodes, and sometimes for PROGRAM nodes (for example, when loaded with •Import). If any identifiers in the node's scope are exported, or any of its statements is an EXPORT, then the result is the namespace created in order to evaluate the node. If a result is required but the namespace case doesn't apply, then the last STMT node must be an EXPR and its result is used. The statement EXPR evaluates some APL code and possibly assigns the results, while nothing evaluates any subject or Derv terms it contains but discards the results. An EXPORT statement performs no action.

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