Hst hst

Comments and changes to this ticket

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  Douglas Creager September 2nd, 2008 @ 07:10 PM

  (from [2a3f31e387e7b41c1856ff79a47ad5bfebdea5cc]) CSPM environments

  An environment is the symbol table that hold CSPM definitions. They provide a standard mapping between identifiers and the expressions that define them. Environments can also have an optional parent, which allows nested scoping; if an identifier is not found in the current environment, we then proceed to look for it in the containing environment.

  This patch introduces the basic API for creating and using environments, but does not extend the evaluation rules to use them.

  Lighthouse: [#11] http://github.com/dcreager/hst/c...

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  Douglas Creager September 2nd, 2008 @ 07:11 PM

  (from [37739ef6e867fa53cb039c707bf15d4e1affd1ba]) Flattening the Expression type

  Before, we had separate datatypes for each “class” of expression; for instance, a Number type for any expression that always evaluates to a number. The Expression type was then defined as a sum type across all of these subtypes.

  This patch flattens things so that there's only a single Expression type. This simplifies things by removing a level of indirection in the type definitions, and also will make it easier to define “bound expressions” as we implement static-scoped environments.

  Lighthouse: [#11] http://github.com/dcreager/hst/c...

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  Douglas Creager September 2nd, 2008 @ 07:11 PM

  (from [260a78539f5808c2553f028caf28fc47e57ddb0c]) Let bindings

  This patch introduces evaluation rules for let bindings and variable references. Currently, this is the only way to define the value for a variable.

  Lighthouse: [#11] http://github.com/dcreager/hst/c...

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  Douglas Creager September 2nd, 2008 @ 07:12 PM

  • State changed from “new” to “resolved”

  (from [5767f91d2daf37310ef12fbfd1c7f0617780cc46]) Evaluation rules for lambdas

  This patch introduces lambdas and application statements. This requires carrying around bound expressions as regular expressions, since the actual parameters to an application are already bound, but we need to add those actual parameters to the environment created for evaluating the lambda body.

  Lighthouse: [#11 state:resolved] http://github.com/dcreager/hst/c...