25 lines
714 B
Go
25 lines
714 B
Go
package expr
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// Ctx contains all the Macros and Identifiers available. A Ctx is based on the
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// parent it was created from. If the current Ctx doesn't have a particular key
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// being looked up, the parent is called instead, and so on. A consequence of
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// this is that keys in the children take precedence over the parent's
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type Ctx struct {
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Parent *Ctx
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Macros map[Macro]func(Expr) (Expr, error)
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}
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// GetMacro returns the first instance of the given of the given Macro found. If
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// not found nil is returned.
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func (c *Ctx) GetMacro(m Macro) func(Expr) (Expr, error) {
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if c.Macros != nil {
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if fn, ok := c.Macros[m]; ok {
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return fn
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}
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}
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if c.Parent != nil {
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return c.Parent.GetMacro(m)
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}
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return nil
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}
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