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51 lines
987 B
51 lines
987 B
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan. |
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/ |
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package expr |
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import ( |
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"fmt" |
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) |
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//!+Check |
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func (v Var) Check(vars map[Var]interface{}) error { |
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vars[v] = true |
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return nil |
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} |
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func (literal) Check(vars map[Var]interface{}) error { |
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return nil |
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} |
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func (u unary) Check(vars map[Var]interface{}) error { |
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return u.x.Check(vars) |
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} |
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func (b binary) Check(vars map[Var]interface{}) error { |
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if err := b.x.Check(vars); err != nil { |
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return err |
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} |
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return b.y.Check(vars) |
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} |
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func (c call) Check(vars map[Var]interface{}) error { |
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arity, ok := numParams[c.fn] |
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if !ok { |
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return fmt.Errorf("unknown function %q", c.fn) |
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} |
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if len(c.args) != arity { |
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return fmt.Errorf("call to %s has %d args, want %d", |
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c.fn, len(c.args), arity) |
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} |
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for _, arg := range c.args { |
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if err := arg.Check(vars); err != nil { |
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return err |
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} |
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} |
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return nil |
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} |
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var numParams = map[string]int{"pow": 2, "sin": 1, "sqrt": 1} |
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//!-Check
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