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Diffstat (limited to 'doc/expression.md')
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diff --git a/doc/expression.md b/doc/expression.md index 754775ea..d5ca2035 100644 --- a/doc/expression.md +++ b/doc/expression.md @@ -2,7 +2,7 @@ # Expression syntax -BQN expressions are the part of [syntax](syntax.md) that describes computations to perform. Programs are mainly made up of expressions with a little organizing material like [blocks](block.md) and [namespaces](namespace.md) around them. This page explains how functions, modifiers, and assignment combine with their inputs. It doesn't describe [constant](syntax.md#constants) and [array](arrayrepr.md#list-literals) literals, which each form a single subject for grammatical purposes. +BQN expressions are the part of [syntax](syntax.md) that describes computations to perform. Programs are mainly made up of expressions with a little organizing material like [blocks](block.md) and [namespaces](namespace.md) around them. This page explains how functions, modifiers, and assignment combine with their inputs. It doesn't describe [constant](syntax.md#constants) and [array](arrayrepr.md#array-literals) literals, which each form a single subject for grammatical purposes. The [first tutorial](../tutorial/expression.md) also covers how to build and read BQN expressions. @@ -54,7 +54,7 @@ Primitive tokens, since they have a fixed value, always have a role that matches Variable names can be written in any case and with underscores added, and these changes don't affect what [identifier](lexical.md) the name refers to. `ab`, `aB`, `AB`, and `_a_B_` are all the same variable. However, the spelling—specifically the first and last characters—determine the variable's role. A lowercase first letter indicates a subject, and an uppercase first letter makes it a function. A leading underscore (regardless of the following character) indicates a 1-modifier, and both leading and trailing underscores makes a 2-modifier. -Besides these, character, string, and [list literals](arrayrepr.md#list-literals) always have a subject role, and the role of a [block](block.md) is determined by its type, which depends either on the header it has or which special variables it uses. +Besides these, character, string, and [array literals](arrayrepr.md#array-literals) always have a subject role, and the role of a [block](block.md) is determined by its type, which depends either on the header it has or which special variables it uses. The role of a compound expression, formed by applying an operation to some inputs, depends on the operation applied. This system is discussed in the remaining sections below. @@ -114,6 +114,12 @@ The left hand side of assignment in a subject expression can be *compound*, so t s +Array destructuring using `[]` is also possible: it's equivalent to splitting the right-hand side with `<˘` and then applying list destructuring. + + [t,u] ← ↕2‿3 + + u + Namespace destructuring uses an overlapping syntax, fully described in [its own section](namespace.md#imports). The left hand side is a list of names or aliases `to⇐from`. q‿r ↩ {q⇐2+r⇐0.5} ⋄ q |