14 Units

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14 | Units
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▼ | 14 | Units

14.1 | Signatures and Units
14.2 | Invoking Units
14.3 | Linking Units
14.4 | First-Class Units
14.5 | Whole-module Signatures and Units
14.6 | Contracts for Units
14.7 | unit versus module

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### 14`` Units (Components)

Units organize a program into separately compilable and reusable components. A unit resembles a procedure in that both are first-class values that are used for abstraction. While procedures abstract over values in expressions, units abstract over names in collections of definitions. Just as a procedure is called to evaluate its expressions given actual arguments for its formal parameters, a unit is invoked to evaluate its definitions given actual references for its imported variables. Unlike a procedure, however, a unit’s imported variables can be partially linked with the exported variables of another unit prior to invocation. Linking merges multiple units together into a single compound unit. The compound unit itself imports variables that will be propagated to unresolved imported variables in the linked units, and re-exports some variables from the linked units for further linking.

14.1 Signatures and Units
14.2 Invoking Units
14.3 Linking Units
14.4 First-Class Units
14.5 Whole-module Signatures and Units
14.6 Contracts for Units
14.6.1 Adding Contracts to Signatures
14.6.2 Adding Contracts to Units
14.7 unit versus module

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