我在试图弄清楚修改报价并评估它们。在这里,我从基础开始,尝试使用Quotations API创建报价。报价绑定OK,但评估时出现错误。从PowerPack评估合成报价表达式时出错
#r @"FSharpPowerPack-2.0.0.0\bin\FSharp.PowerPack.dll"
#r @"FSharpPowerPack-2.0.0.0\bin\FSharp.PowerPack.Linq.dll"
open Microsoft.FSharp.Quotations
open Microsoft.FSharp.Linq.QuotationEvaluation
open Microsoft.FSharp.Linq
let hardway =
Expr.Let(
new Var("x", typeof<int>),
Expr.Value(10),
Expr.GlobalVar("x").Raw)
hardway.EvalUntyped()
Binding session to 'FSharp.PowerPack.Linq.dll'...
System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at Microsoft.FSharp.Collections.MapTreeModule.find[TValue,a](IComparer`1 comparer, TValue k, MapTree`2 m)
at Microsoft.FSharp.Linq.QuotationEvaluation.ConvExpr(ConvEnv env, FSharpExpr inp) in d:\codeplex\fspowerpack\May2010\src\FSharp.PowerPack.Linq\Linq.fs:line 459
at Microsoft.FSharp.Linq.QuotationEvaluation.ConvExpr(ConvEnv env, FSharpExpr inp) in d:\codeplex\fspowerpack\May2010\src\FSharp.PowerPack.Linq\Linq.fs:line 704
at Microsoft.FSharp.Linq.QuotationEvaluation.ConvExpr(ConvEnv env, FSharpExpr inp) in d:\codeplex\fspowerpack\May2010\src\FSharp.PowerPack.Linq\Linq.fs:line 677
at Microsoft.FSharp.Linq.QuotationEvaluation.CompileImpl[a](a e, Boolean eraseEquality) in d:\codeplex\fspowerpack\May2010\src\FSharp.PowerPack.Linq\Linq.fs:line 837
at Microsoft.FSharp.Linq.QuotationEvaluation.Expr.EvalUntyped(FSharpExpr) in d:\codeplex\fspowerpack\May2010\src\FSharp.PowerPack.Linq\Linq.fs:line 854
at <StartupCode$FSI_0009>[email protected]()
Stopped due to error
太好了,谢谢。你的第二点很重要,因为如果没有指定类型,则抛出相同的异常。 – yanta 2010-11-19 08:10:02