mirror of
https://github.com/johnkerl/miller.git
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101 lines
3.5 KiB
Go
101 lines
3.5 KiB
Go
// ================================================================
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// CST build/execute for AST operator/function nodes.
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//
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// Operators and functions are semantically the same thing -- they differ only
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// syntactically. Binary operators are infix, like '1+2', while functions are
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// prefix, like 'max(1,2)'. Both parse to the same AST shape.
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// ================================================================
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package cst
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import (
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"github.com/johnkerl/miller/internal/pkg/dsl"
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"github.com/johnkerl/miller/internal/pkg/lib"
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)
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// ----------------------------------------------------------------
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// Function lookup:
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//
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// * Try builtins first
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// * Absent a match there, try UDF lookup (i.e. the UDF has been defined before being called)
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// * Absent a match there:
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// o Make a UDF-placeholder node with present signature but nil function-pointer
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// o Append that node to CST to-be-resolved list
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// o On a next pass, we will walk that list resolving against all encountered
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// UDF definitions. (It will be an error then if it's still unresolvable.)
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func (root *RootNode) BuildFunctionCallsiteNode(astNode *dsl.ASTNode) (IEvaluable, error) {
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lib.InternalCodingErrorIf(
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astNode.Type != dsl.NodeTypeFunctionCallsite &&
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astNode.Type != dsl.NodeTypeOperator,
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)
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lib.InternalCodingErrorIf(astNode.Token == nil)
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lib.InternalCodingErrorIf(astNode.Children == nil)
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functionName := string(astNode.Token.Lit)
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// Special-case the dot operator, which is:
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// * string + string, with coercion to string if either side is int/float/bool/etc.;
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// * map attribute access, if the left-hand side is a map.
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if functionName == "." {
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dotCallsiteNode, err := root.BuildDotCallsiteNode(astNode)
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if err != nil {
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return nil, err
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}
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return dotCallsiteNode, nil
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// Look for a builtin function with the given name.
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builtinFunctionCallsiteNode, err := root.BuildBuiltinFunctionCallsiteNode(astNode)
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if err != nil {
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return nil, err
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}
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if builtinFunctionCallsiteNode != nil {
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return builtinFunctionCallsiteNode, nil
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// Look for a user-defined function with the given name.
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callsiteArity := len(astNode.Children)
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udf, err := root.udfManager.LookUp(functionName, callsiteArity)
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if err != nil {
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return nil, err
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}
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// AST snippet for '$z = f($x, $y)':
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// * Assignment "="
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// * DirectFieldValue "z"
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// * FunctionCallsite "f"
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// * DirectFieldValue "x"
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// * DirectFieldValue "y"
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//
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// Here we need to make an array of our arguments at the callsite, to be
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// paired up with the parameters within he function definition at runtime.
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argumentNodes := make([]IEvaluable, callsiteArity)
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for i, argumentASTNode := range astNode.Children {
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argumentNode, err := root.BuildEvaluableNode(argumentASTNode)
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if err != nil {
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return nil, err
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}
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argumentNodes[i] = argumentNode
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}
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if udf == nil {
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// Mark this as unresolved for an after-pass to see if a UDF with this
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// name/arity has been defined farther down in the DSL expression after
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// this callsite. This happens example when a function is called before
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// it's defined.
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udf = NewUnresolvedUDF(functionName, callsiteArity)
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udfCallsiteNode := NewUDFCallsite(argumentNodes, udf)
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root.rememberUnresolvedFunctionCallsite(udfCallsiteNode)
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return udfCallsiteNode, nil
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} else {
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udfCallsiteNode := NewUDFCallsite(argumentNodes, udf)
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return udfCallsiteNode, nil
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}
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}
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